Química Inorgánica

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Unconventional coordination modes of carboranyl phosphine-iminophosphorane ligands
(Royal Society of Chemistry, 2025-10-02) Rodríguez Rey, José Luis; Vázquez Carballo, Irene; Sousa Pedrares, Antonio; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
A series of new carboranyl phosphine–iminophosphorane ligands were obtained and characterized. The ligands present a flexible three-atom spacer between (P,N) donor atoms, derived from the diphosphine dppe. The ligands include examples of C-carboranyl derivatives (ligands L1–L3) and B3-carboranyl derivatives (ligands L4 and L5), to compare the different effect of these electron-withdrawing groups. An organic analog was also prepared (ligand L6) for comparison purposes. The analysis of the structures of their dichloride palladium(II) complexes using several techniques, including X-ray diffraction, reveals that the carboranyl group can affect the coordinating ability of the attached nitrogen atom. Thus, although organic phosphine–iminophosphorane ligands always show the (P,N) chelating mode, providing both sites are available, the new carboranyl ligands give rise to a surprising variety of coordination modes: the expected (P,N) chelating mode, the unusual P-terminal mode and the unprecedented (P,N) bridging mode. The comparison of these structures with organic analogues and with the carboranyl ligands derived from the diphosphine dppm indicates that the length of the spacer between the donor atoms is an important variable for the coordination mode of the ligand, once the coordinating strength of the nitrogen atom is reduced by effect of the carborane cage.
Libro de Resumos da V Xuntanza de Investigador@s Nov@s no ámbito da química (XINQ_5)
(2025) Xuntanza Investigador@s Nov@s no ámbito da Química; Universidade de Santiago de Compostela. Facultade de Química; Martínez-Calvo, Miguel; Montes Goyanes, Rosa; Vázquez Vázquez, Carlos; Rumbo Gómez, Antonio
A XINQ é un espazo de encontro no que as investigadoras e investigadores novos que desenvolven o seu traballo no ámbito da química poden dalo a coñecer ao resto da comunidade universitaria. A xuntanza está pensada para que @s nov@s investigador@s entendan que se pode explicar a ciencia, a química no noso caso, en lingua galega ao mesmo tempo que desenvolven as súas capacidades de comunicación en público. A xuntanza desenvólvese a través dunha serie comunicacións orais de carácter divulgativo onde, en galego, expoñen os aspectos máis significativos e xerais da investigación que realizan no seu máster ou doutoramento. Nesta cuarta edición, o comité organizador considera que a XINQ se consolidou xa como un espazo para a difusión da investigación no ámbito da química na nosa universidade en galego. Nesta xuntanza pódense encontrar participantes procedentes da maioría dos centros de investigación e facultades da nosa institución, pero ten máis importancia, na nosa opinión, a participación de estudantes que non teñen o galego como lingua materna. El@s ofrécenos o exemplo da importancia que lle dan as persoas á lingua no proceso de integración e como ven nela un vinculo sentimental fundamental na nosa sociedade. Dende a Comisión de Normalización Lingüística da Facultade de Química débese reflexionar sobre a participación do seu profesorado nesta actividade. Sería positivo que en cada edición unha parella de profesores puidesen expoñer a investigación realizada ou un tema científico de actualidade de xeito divulgativo en lingua galega. Deste xeito, co tempo, poderían animarse a desenvolver a súa actividade docente en galego utilizado en pouca medida na nosa facultade.
A Dinuclear Copper(II) Complex Electrochemically Obtained via the Endogenous Hydroxylation of a Carbamate Schiff Base Ligand: Synthesis, Structure and Catalase Activity
(MDPI, 2024-02-10) Fernández-Fariña, Sandra; Velo Heleno, Isabel; Rodríguez Silva, Laura; Maneiro Maneiro, Marcelino; González Noya, Ana María; Pedrido Castiñeiras, Rosa; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
In the present work, we report a neutral dinuclear copper(II) complex, [Cu2(L1)(OH)], derived from a new [N,O] donor Schiff base ligand L1 that was formed after the endogenous hydroxylation of an initial carbamate Schiff base H2L coordinated with copper ions in an electrochemical cell. The copper(II) complex has been fully characterized using different techniques, including X-ray diffraction. Direct current (DC) magnetic susceptibility measurements were also performed at variable temperatures, showing evidence of antiferromagnetic behavior. Its catalase-like activity was also tested, demonstrating that this activity is affected by temperature.
POM-Based Water Splitting Catalyst Under Acid Conditions Driven by Its Assembly on Carbon Nanotubes
(Wiley, 2025-11-26) Quirós Díez, Eugenia Pilar; Guillén Soler, Melanie; Herreros Lucas, Carlos; López Moreno, Alejandro; Vila Fungueiriño, José Manuel; Llamas Saiz, Antonio Luis; Strutyński, Karol; Melle Franco, Manuel; Giménez López, María del Carmen; Universidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS); Universidade de Santiago de Compostela. Departamento de Química Física
Development of efficient and stable bifunctional electrocatalysts for water electrolysis under acidic conditions is essential for sustainable hydrogen production. A novel vanadium polyoxometalate (POM)-based material, Na4(H2O)12[(CH2OH)3CNH3]2[V10O28]·4H2O (1) is presented, incorporating non-innocent cations and whose electrocatalytic activity can be switched from the production of oxygen to hydrogen through its assembly on carbon nanotubes (CNT). A physical mixture (1/CNT) shows remarkable oxygen evolution reaction (OER) activity, with an overpotential of 0.34 V at 10 mA cm−2, outperforming commercial IrO2 (0.45 V) and approaching Ir/C (0.31 V), with 80% Faradaic efficiency. In contrast, directed assembly (1@CNT) unlocks TRIS ⁺= [(CH2OH)3CNH3]⁺ groups functionality, enabling high hydrogen evolution reaction (HER) efficiency, with an onset potential of −0.07 V, close to Pt/C, and 94% Faradaic efficiency. Mechanistic studies, strongly supported by in-operando confocal microscopy and theoretical calculations, reveal that the modulation of crystal interactions and the local microenvironment is key to orchestrating the OER/HER tuning. OER is proposed to proceed via an alcohol oxidation reaction (AOR), while HER benefits from TRIS⁺ moieties acting as a “proton sponge”. This work provides a compelling approach for rational design of bifunctional molecular electrocatalysts based on earth-abundant elements and controlled nanoassembly, with clear relevance for advancing green hydrogen production technologies.
Understanding the Factors That Influence the Antioxidant Activity of Manganosalen Complexes with Neuroprotective Effects
(MDPI, 2024-02-22) Rouco Méndez, Lara; Alvariño Romero, Rebeca; Alfonso Rancaño, María Amparo; Fernández-Fariña, Sandra; González Noya, Ana María; Martínez Calvo, Miguel; Pedrido Castiñeiras, Rosa; Rodríguez Silva, Laura; Maneiro Maneiro, Marcelino; Universidade de Santiago de Compostela. Departamento de Química Inorgánica; Universidade de Santiago de Compostela. Departamento de Fisioloxía; Universidade de Santiago de Compostela. Departamento de Farmacoloxía, Farmacia e Tecnoloxía Farmacéutica
Manganosalen complexes are a class of catalytic antioxidants with beneficial effects against different neurological disorders according to various in vitro and in vivo studies. The interest in the factors that determine their antioxidant activity is based on the fact that they are key to achieving more efficient models. In this work, we report a set of new manganosalen complexes, thoroughly characterized in the solid state and in solution by different techniques. The chelating Schiff base ligands used were prepared from condensation of different substituted hydroxybenzaldehydes with 1,2-diaminoethane and 1,3-diaminopropane. The antioxidant activity of the new models was tested through superoxide dismutase and catalase probes in conjunction with the studies about their neuroprotective effects in human SH-SY5Y neuroblastoma cells in an oxidative stress model. The ability to scavenge excess reactive oxygen species (ROS) varied depending on the manganosalen models, which also yielded different improvements in cell survival. An assessment of the different factors that affect the oxidant activity for these complexes, and others previously reported, revealed the major influence of the structural factors versus the redox properties of the manganosalen complexes.
Endeavor toward Redox-Responsive Transition Metal Contrast Agents Based on the Cross-Bridge Cyclam Platform
(American Chemical Society, 2024-01-10) Uzal-Varela, Rocío; Rodríguez-Rodríguez, Aurora; Lalli, Daniela; Valencia, Laura; Maneiro Maneiro, Marcelino; Botta, Mauro; Iglesias, Emilia; Esteban-Gómez, David; Angelovski, Goran; Platas-Iglesias, Carlos; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
We present the synthesis and characterization of a series of Mn(III), Co(III), and Ni(II) complexes with cross-bridge cyclam derivatives (CB-cyclam = 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) containing acetamide or acetic acid pendant arms. The X-ray structures of [Ni(CB-TE2AM)]Cl2·2H2O and [Mn(CBTE1AM)(OH)](PF6)2 evidence the octahedral coordination of the ligands around the Ni(II) and Mn(III) metal ions, with a terminal hydroxide ligand being coordinated to Mn(III). Cyclic voltammetry studies on solutions of the [Mn(CBTE1AM)(OH)]2+ and [Mn(CB-TE1A)(OH)]+ complexes (0.15 M NaCl) show an intricate redox behavior with waves due to the MnIII/MnIV and MnII/MnIII pairs. The Co(III) and Ni(II) complexes with CB-TE2A and CB-TE2AM show quasireversible features due to the CoIII/CoII or NiII/NiIII pairs. The [Co(CBTE2AM)]3+ complex is readily reduced by dithionite in aqueous solution, as evidenced by 1H NMR studies, but does not react with ascorbate. The [Mn(CBTE1A)(OH)]+ complex is however reduced very quickly by ascorbate following a simple kinetic scheme (k0 = k1[AH−], where [AH−] is the ascorbate concentration and k1 = 628 ± 7 M−1 s−1). The reduction of the Mn(III) complex to Mn(II) by ascorbate provokes complex dissociation, as demonstrated by 1H nuclear magnetic relaxation dispersion studies. The [Ni(CB-TE2AM)]2+ complex shows significant chemical exchange saturation transfer effects upon saturation of the amide proton signals at 71 and 3 ppm with respect to the bulk water signal.
Enemies or Allies? Hormetic and Apparent Non-Dose-Dependent Effects of Natural Bioactive Antioxidants in the Treatment of Inflammation
(MDPI, 2024-02-04) Barreiro Sisto, Uxía; Fernández-Fariña, Sandra; González Noya, Ana María; Pedrido Castiñeiras, Rosa; Maneiro Maneiro, Marcelino; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
This review aims to analyze the emerging number of studies on biological media that describe the unexpected effects of different natural bioactive antioxidants. Hormetic effects, with a biphasic response depending on the dose, or activities that are apparently non-dose-dependent, have been described for compounds such as resveratrol, curcumin, ferulic acid or linoleic acid, among others. The analysis of the reported studies confirms the incidence of these types of effects, which should be taken into account by researchers, discarding initial interpretations of imprecise methodologies or measurements. The incidence of these types of effects should enhance research into the different mechanisms of action, particularly those studied in the field of basic research, that will help us understand the causes of these unusual behaviors, depending on the dose, such as the inactivation of the signaling pathways of the immune defense system. Antioxidative and anti-inflammatory activities in biological media should be addressed in ways that go beyond a mere statistical approach. In this work, some of the research pathways that may explain the understanding of these activities are revised, paying special attention to the ability of the selected bioactive compounds (curcumin, resveratrol, ferulic acid and linoleic acid) to form metal complexes and the activity of these complexes in biological media.
Luminescent Thermometer Based on a Praseodymium(iii) Cyanide-Based Metal-Organic Framework
(American Chemical Society, 2024-12-19) Lalioti, Nikolia; Zygouri, Eleni; Nastopoulos, Vassilis; Panagiotou, Nikos; Brites, Carlos D. S.; Carlos, Luis D.; Corredoira Vázquez, Julio; Tangoulis, Vassilis; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
Trivalent lanthanide ions have emerged as promising candidates for precise and remote temperature sensing. Among them, Pr3+-based luminescent thermometers remain underexplored, particularly those operating in the near-infrared (NIR) spectral region. This work presents the synthesis and thorough characterization of a novel Pr3+-based coordination polymer, {[Pr2IIIPt3II(CN)12(4,4′-bpyO2)4(H2O)6]·4H2O}n (1), as a rare example of Pr3+ luminescent thermometry. Coordination between Pr3+ ions, cyanido-bridged Pt2+ centers, and 4,4′-bpyO2 ligands enables efficient energy transfer, producing luminescence in visible and near-infrared regions. The polymer demonstrates distinct temperature-dependent luminescence over a wide range (12-386 K), with relative thermal sensitivities of ≅1%·K-1 and a minimum temperature uncertainty of 0.2 K.
Geometry-Driven Field-Induced Single-Ion Magnetism in Hexagonal Bipyramidal Tb3+ and Ho3+ Complexes
(American Chemical Society, 2025-10-11) González Barreira, Cristina; Oreiro Martínez, Paula; Fondo Busto, María Matilde; Corredoira Vázquez, Julio; García Deibe, Ana María; Sanmartín Matalobos, Jesús; Aravena, Daniel; Colacio, Enrique; Universidade de Santiago de Compostela. Departamento de Química Inorgánica; Universidade de Santiago de Compostela. Instituto de Materiais (iMATUS)
The synthesis of the precursors [Ln(LN6en)(CH3COO)2](BPh4)·nH2O (Ln = Tb, n = 0, 1; Ln = Ho, n = 1, 2·H2O), followed by a ligand exchange reaction with triphenylsilanolate, results in the isolation of the complexes {[Ln(LN6en)(OSiPh3)2](BPh4)}·2CH2Cl2 (Ln = Tb, 3·2CH2Cl2; Ln = Ho, 4·2CH2Cl2). Single-crystal X-ray diffraction studies of 3·2CH2Cl2 and 4·2CH2Cl2 revealed that both compounds adopt a hexagonal bipyramidal geometry. Magnetic characterization shows that the complexes behave as single-ion magnets (SIMs) under an optimal applied field of 2000 Oe. Notable, these are the first reported Tb3+ and Ho3+ complexes with a hexagonal bipyramidal coordination geometry to exhibit such magnet-like behavior. Furthermore, they constitute the first field-induced Tb3+ and Ho3+ SIMs incorporating a macrocyclic ligand in a nonsandwich topology. Magnetic measurements indicate that the applied field only partially suppresses quantum tunneling of magnetization (QTM) and that at higher temperatures magnetic relaxation is dominated by the Raman process rather than the Orbach mechanism. These experimental observations are supported by ab initio calculations, which provide detailed insights into the electronic structure, including the splitting of f-orbital energy levels, thereby elucidating the origin of the observed magnetic behavior in both cases
Application of the aza-Wittig reaction for the synthesis of carboranyl Schiff bases, benzothiazoles and benzoselenazolines
(Royal Society of Chemistry, 2025-01-09) Crujeiras Barral, Pablo; Vázquez Carballo, Irene; Sousa Pedrares, Antonio; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
The aza-Wittig reaction was successfully applied to the synthesis of carboranyl-imines, which are difficult to obtain by classical methods. A variety of functionalized carboranyl Schiff bases was obtained proving the great scope of the methodology. All compounds were fully characterized, including the solid-state structures of six of them. The aza-Wittig reaction was modified to permit the synthesis in one step of carboranyl-benzothiazole and carboranyl-benzoselenazoline derivatives. The stability studies show that the carboranyl-imines and benzothiazole promote deboronation to the nido-derivatives, which is achieved by simple reaction with methanol or protic solvents. The structures of the nido-derivatives were also studied by X-ray diffraction. In contrast, the saturated derivatives, amine and benzoselenazoline, do not promote deboronation and are stable in protic solvents.
Exploring the Biological Properties of Zn(II) Bisthiosemicarbazone Helicates
(MDPI, 2023-01-23) Fernández-Fariña, Sandra; Velo Heleno, Isabel; Carballido, Rocío; Martínez-Calvo, Miguel; Barcia Vieitez, Ramiro; Palacios, Òscar; Capdevila, Mercè; González Noya, Ana María; Pedrido Castiñeiras, Rosa; Universidade de Santiago de Compostela. Departamento de Química Inorgánica; Universidade de Santiago de Compostela. Departamento de Bioquímica e Bioloxía Molecular
The design of artificial helicoidal molecules derived from metal ions with biological properties is one of the objectives within metallosupramolecular chemistry. Herein, we report three zinc helicates derived from a family of bisthiosemicarbazone ligands with different terminal groups, Zn2(LMe)2∙2H2O 1, Zn2(LPh)2∙2H2O 2 and Zn2(LPhNO2)2 3, obtained by an electrochemical methodology. These helicates have been fully characterized by different techniques, including X-ray diffraction. Biological studies of the zinc(II) helicates such as toxicity assays with erythrocytes and interaction studies with proteins and oligonucleotides were performed, demonstrating in all cases low toxicity and an absence of covalent interaction with the proteins and oligonucleotides. The in vitro cytotoxicity of the helicates was tested against MCF-7 (human breast carcinoma), A2780 (human ovarian carcinoma cells), NCI-H460 (human lung carcinoma cells) and MRC-5 (normal human lung fibroblasts), comparing the IC50 values with cisplatin. We will try to demonstrate if the terminal substituent of the ligand precursor exerts any effect in toxicity or in the antitumor activity of the zinc helicates
Schiff Bases Functionalized with T-Butyl Groups as Adequate Ligands to Extended Assembly of Cu(II) Helicates
(MDPI, 2023-05-12) Fernández-Fariña, Sandra; Velo Heleno, Isabel; Martínez-Calvo, Miguel; Maneiro Maneiro, Marcelino; González Noya, Ana María; Pedrido Castiñeiras, Rosa; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
The study of the inherent factors that influence the isolation of one type of metallosupramolecular architecture over another is one of the main objectives in the field of Metallosupramolecular Chemistry. In this work, we report two new neutral copper(II) helicates, [Cu2(L1)2]·4CH3CN and [Cu2(L2)2]·CH3CN, obtained by means of an electrochemical methodology and derived from two Schiff-based strands functionalized with ortho and para-t-butyl groups on the aromatic surface. These small modifications let us explore the relationship between the ligand design and the structure of the extended metallosupramolecular architecture. The magnetic properties of the Cu(II) helicates were explored by Electron Paramagnetic Resonance (EPR) spectroscopy and Direct Current (DC) magnetic susceptibility measurements
Coordination chemistry of Amine Bis(phenolate) Cobalt(II), Nickel(II), and Copper(II) complexes
(ACS, 2006-08-23) Rodríguez Silva, Laura; Labisbal Viqueira, María Elena; Sousa Pedrares, Antonio; García Vázquez, José Arturo; Romero López-Grado, Jaime; Durán Carril, María Luz; Real, José A.; Sousa, Antonio; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
Cobalt(II), nickel(II), and copper(II) (1, 2, and 3) complexes of the dianionic form of the bis(phenolate) ligand N,N-bis(3,4-dimethyl-2-hydroxybenzyl)-N‘,N‘-dimethylethylenediamine (H2L) have been synthesized by electrochemical oxidation of the appropriate metal in an acetonitrile solution of the ligand. When copper is used as the anode, the addition of 1,10-phenanthroline to the electrolytic phase gave rise to a different compound [CuL]2·2CH3CN (4). The compounds [CoL]2·2CH3CN (1), [Ni2L2(H2O)]·H2O (2), [CuL]2·3H2O (3), and [CuL]2·2CH3CN (4) were characterized by microanalysis, IR, electronic spectroscopy, FAB mass spectrometry, magnetic measurements and by single-crystal X-ray diffraction. The crystal structures show that the complexes have a dinuclear structure. In compounds 1, 3, and 4, two metal ions are coordinated by the two amine nitrogens and the two phenol oxygen atoms of a deprotonated pendant phenol ligand, with one phenolic oxygen atom from ligand acting as a bridge. In compounds 1 and 3, each metal center has a geometry that is closest to trigonal bipyramidal. Magnetic susceptibility data for both compounds show an antiferromagnetic coupling with 2J = −15 cm-1 for the cobalt(II) complex and a strong antiferromagnetic coupling with 2J = −654 cm-1 for the copper(II) complex. However, in 4 the geometry around the metal is closer to square pyramidal and the compound shows a lower antiferromagnetic coupling (2J = −90 cm-1) than in 3. The nickel atoms in the dimeric compound 2 are hexacoordinate. The NiN2O4 chromophore has a highly distorted octahedral geometry. In this structure, a dianionic ligand binds to one nickel through the two amine nitrogen atoms and the two oxygen atoms and to an adjacent nickel via one of these oxygen atoms. The nickel atoms are linked through a triple oxygen bridge involving two phenolic oxygens, each from a different ligand, and an oxygen atom from a water molecule. The two nickel ions in 2 are ferromagnetically coupled with 2J = 19.8 cm-1
Novel trans-disubstituted hexaaza-macrocyclic ligands containing pyridine head units: Synthesis, disubstitution and colorimetric properties
(Elsevier, 2016-03-31) Lamelas, Rodrigo; García, Verónica; Liñares, Araceli; Bastida de la Calle, Rufina; Labisbal Viqueira, María Elena; Fernández Lodeiro, Adrián; Lodeiro, Carlos; Núñez González, Cristina; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
A trans-N,N′-methylated hexaazamacrocycle precursor L3, derived from the hexadentate polyamine macrocycle L (Py2[18]aneN6), was synthesized for the first time. The crystal structures of the intermediates L1·8H2O and L2I2·H2O showing two trans quaternary nitrogen atoms have also been determined by single-crystal X-ray crystallography. By the alkylation of the trans secondary amines present in L3, two novel macrocyclic molecular probes 1 and 2 linked to two nitrophenylurea and two nitrophenylthiourea groups, respectively, are reported. Crystals of 1·2CDCl3 suitable for single-crystal X-ray diffraction analysis were also obtained. The coordination ability of compounds 1 and 2 toward hydrated nitrate salts of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) was studied. Their responses toward different anions (fluoride (F−), chloride (Cl−), bromide (Br−), iodide (I−), hydroxide (OH−), acetate (AcO−), cyanide (CN−), dihydrogen phosphate (H2PO4−), nitrate (NO3−) and perchlorate (ClO4−)) in DMSO solution were evaluated by UV–vis absorption spectroscopy. The immobilization of probe 1 in cellulose supported systems to evaluate its efficiency in the fast recognition of different anions (F−, AcO−, CN−, H2PO4−) in aqueous phase was also described
Electrochemical synthesis and structural characterization of Co(II), Ni(II) and Cu(II) complexes of N,N-bis(4,5-dimethyl-2-hydroxybenzyl)- N-(2-pyridylmethyl)amine
(Royal Society of Chemistry, 2009-08-24) Labisbal Viqueira, María Elena; Rodríguez Silva, Laura; Souto, Óscar; Sousa Pedrares, Antonio; García Vázquez, José Arturo; Romero, Jaime; Sousa, Antonio; Yañez, Matilde; Orallo, Francisco; Real, José A.; Universidade de Santiago de Compostela. Departamento de Química Inorgánica; Universidade de Santiago de Compostela. Departamento de Farmacoloxía
The electrochemical oxidation of anodic metal (cobalt, nickel or copper) in a cell containing an acetonitrile solution of the ligand N,N-bis(4,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine (H2L) affords complexes [Co2L2]·H2O (1), [Ni3L3] (2) and [Cu2L2] 3H2O (4). On using nickel as the anode and the addition to the solution electrolytic phase of the amount of water necessary to saturate the solution, the electrolytic process gave rise to the new compound [Ni2L2(H2O)1.5]·CH3CN (3). Compounds 1 and 4 are dimeric and the metal atoms are pentacoordinated. Compound 3 also consists of dimeric neutral molecules with the nickel atoms in both penta- and hexacoordinated environments. The crystal structure of 2 shows the presence of a trimeric compound in which the nickel atoms are hexacoordinated. Electronic, IR and FAB spectra of the complexes are discussed and related to the structural information. The magnetic behavior of 1–4 denotes the occurrence of intramolecular antiferromagnetic interactions. The values obtained for the coupling constant J are −4.2 cm−1, −5.3 cm−1, −30 cm−1 and −4.7 cm−1 for 1, 2, 3 and 4, respectively. These values are in full agreement with the structural characteristics of the compounds. The catalytic activity of the complexes towards the decomposition of hydrogen peroxide (catalase activity) was also studied.
Electrochemical Conversion of 5-Hydroxymethylfurfural to 2,5-Furandicarboxaldehyde Using Mn(III)–Schiff Base Catalysts
(MDPI, 2025-02-01) Barreiro Sisto, Uxía; Fernández-Fariña, Sandra; Fernández García, María Isabel; González Noya, Ana María; Velo Heleno, Isabel; Maneiro Maneiro, Marcelino; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
2,5-furandicarboxaldehyde (DFF) is one of the most promising biomass-based building blocks for the synthesis of biobased polymers. DFF can be obtained from 5-hydroxymethylfurfural (HMF), a fructose derivate, and it is a key molecule in the sequence of reactions of furan chemistry to develop biobased plastics. In this frame, four manganese(III)–Schiff base complexes 1–4 have been obtained. The general formula for the complexes, MnLn(OCN)(H2O/CH3OH)m (Ln being the Schiff base ligands L1–L4, formed as the result of the condensation of different substituted hydroxybenzaldehydes with diverse diamines, and m = 1–3), has been confirmed by characterization through different analytical and spectroscopic techniques. X-ray crystallographic studies for 1 and 2 showed tetragonally distorted octahedral structures, where the Schiff base was placed in the equatorial coordination positions of the Mn(III) ion. Complexes 1 and 2 behaved as efficient catalysts in the oxidation of HMF to DFF in an electrolytic reaction at pH 8.5, with phosphate buffer at room temperature, with conversion rates of 70–80%. On the other hand, complexes 3 and 4, where the axial position was sterically less accessible, yielded only an 11% conversion of HMF to DFF. The results indicate that a correct selection of metal complexes allows the development of a new efficient way to obtain DFF.
Anion driven tetrel bonding dictated supramolecular architectures of lead(ii) with a zwitterionic form of polydentate N′-(piperidine-1-carbonothioyl)picolinohydrazonamide
(Royal Society of Chemistry, 2024-07-17) Mahmoudi, Ghodrat; García Santos, María Isabel; Castiñeiras Campos, Alfonso; Fernández Vázquez, Roi; Gargari, Masoumeh Servati; Gomila Ribas, Rosa María; Frontera Beccaria, Antonio; Safin, Damir A.; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
Two novel supramolecular heteroleptic complexes [Pb2L2(NO3)2]n (1) and {[Pb3L3](ClO4)3}n·3.25nH2O (2·3.25nH2O), obtained from N′-(piperidine-1-carbonothioyl)picolinohydrazonamide (HL) and Pb(NO3)2 or Pb(ClO4)2 in aqueous methanol are reported. A crucial role of the auxiliary ligand (NO3− vs. ClO4−) was revealed as a driving force for the formation of the resulting architecture of complexes, which, in turn, are dictated by the formation of tetrel bonds. Complex 1 is constructed from heteroleptic dinuclear centrosymmetric species [Pb2L2(NO3)2], which, in turn, are formed from the heteroleptic mononuclear symmetry related [PbL(NO3)] units, linked through a pair of bonds formed between the metal cations and the thioamide nitrogen atoms. The metal cations form a weaker tetrel bond with the symmetry related nitrate atoms, yielding a 1D polymeric chain structure. These chains are interlinked through N–H⋯O hydrogen bonds, formed between the covalently coordinated nitrate oxygen atom and the NH2 hydrogen atom, yielding a 2D supramolecular architecture. Complex 2·3.25nH2O is constructed from the trinuclear species [Pb3L3](ClO4)3. The trinuclear cation is constructed from three [PbL]+ cations interlinked through two Pb–S and two Pb–N bonds, formed with the thiocarbonyl sulfur atoms and the amide nitrogen atoms. The cations [Pb3L3]3+ are interlinked through two Pb–N and two Pb–S bonds yielding a 1D supramolecular polymeric cationic chain {[Pb3L3]3+}n. The two metal cations corresponding to two [PbL]+ units, linked through a pair of the Pb–S bonds, are additionally bridged by two oxygen atoms of one of the perchlorate anions with the formation of two Pb⋯O tetrel bonds. The coordination spheres of the metal cations are filled by one of the oxygen atoms of two different perchlorate anions with the formation of tetrel bonds. One of these perchlorates also forms the N–H⋯O hydrogen bond within the trinuclear unit [Pb3L3](ClO4)3. 1D supramolecular chains {[Pb3L3]3+}n are interlinked through a myriad of hydrogen bonds formed by the perchlorate anions and crystallized water molecules. The tetrel bonds involving the counterions (Pb⋯O) have been also analysed by DFT calculations via a MEP surface plot and 2D maps of electron localization function (ELF), Laplacian of electron density (∇2ρ) and reduced density gradient (RDG), confirming their noncovalent nature.
An extended supramolecular coordination compound produced from PbCl2 and N′- isonicotinoylpicolinohydrazonamide
(Royal Society of Chemistry, 2024-01-24) García Santos, María Isabel; Iglesias Pereiro, Tamara; Labisbal Viqueira, María Elena; Castiñeiras Campos, Alfonso; Eftekhari-Sis, Bagher; Mahmoudi, Ghodrat; Sagan, Filip; Mitoraj, Mariusz P.; Safin, Damir A.; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
We report a heteroleptic complex [PbCl2(HL′)]·MeOH (1·MeOH), obtained from N′-isonicotinoylpicolinohydrazonamide (HL) and PbCl2, where HL′ is a zwitterionic form of HL with the protonated 4-pyridyl and deprotonated amide nitrogen atoms. All the coordination bonds around the Pb2+ cation are collected in one hemisphere, yielding a large space gap, which allows two molecules of 1 to come into close proximity to each other and linked through two Pb⋯Cl tetrel bonds of ∼3.41 Å. As a result, a supramolecular dimeric species [PbCl2(HL′)]2 is formed, which is stabilized by two C–H⋯Pb anagostic and two C–H⋯Cl interactions. The coordination sphere of the Pb2+ cation is completed by the formation of the Pb⋯O tetrel bond with the methanolic oxygen atom. The supramolecular dimeric species are linked through π⋯π(chelate ring) and π⋯π interactions, yielding a 1D supramolecular chain, which is strengthened by N–H⋯Cl hydrogen bonds. These chains are interlinked through a set of hydrogen bonds and weaker interactions. Extensive computational analyses by charge and energy decomposition scheme ETS-NOCV as well as interacting quantum atoms (IQA) allowed us to conclude that most electrostatically dominated noncovalent interactions follow the strength order: Pb⋯O > Pb⋯Cl > N–H⋯Cl > C–H⋯Pb > C–H⋯Cl. Cooperative action of π⋯π and N–H⋯Cl provides an extraordinary dimeric stabilization energy of about −75 kcal mol−1. Finally, an unusual C–H⋯Pb interaction was identified to be attractive despite its long distance (>3.7 Å). Methanol species is found to be engaged not only in Pb⋯O tetrel bonds, but also in hydrogen N–H⋯O bonds and untypical homopolar dihydrogen interactions C–H⋯H–C.
The lead(II)–N'-isonicotinoylpyrazine-2-carbohydrazonamide complex system as a converter of aerial carbon dioxide to carbonate under electrochemical conditions with the formation of a single-component white light-emitting phosphor
(The Royal Society of Chemistry, 2024-07-02) Mahmoudi, Ghodrat; García Santos, María Isabel; Labisbal Viqueira, María Elena; Castiñeiras Campos, Alfonso; Alizadeh, Vali; Gomila, Rosa M.; Frontera, Antonio; Safin, Damir A.; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
In this contribution, a novel binuclear heteroleptic complex [Pb2L2(CO3)]·2CH3CN·2MeOH (1·2CH3CN·2MeOH) is reported, which was fabricated by electrochemical oxidation of a lead anode under an ambient atmosphere in a CH3CN : MeOH solution of N′-isonicotinoylpyrazine-2-carbohydrazonamide (HL). The CO32− anion was produced from the conversion of aerial CO2 by the Pb2+–L complex system under electrochemical conditions. In the structure of 1, ligand L exhibits a tridentate pincer-like N,N′,O-coordination mode, while the CO32− anion exhibits a tetradentate bridging coordination mode with one of the oxygen atoms exhibiting a bridging μ-coordination mode. The metal cations in the structure of 1 are in a five-membered N2O3 coordination environment, formed by covalent bonds. The molecular structure of 1·2CH3CN·2MeOH is stabilized by a pair of intermolecular Pb⋯N tetrel bonds formed with one of the NH2 nitrogen atoms of an adjacent complex molecule and with the acetonitrile nitrogen atom, and one Pb⋯O tetrel bond formed with the carbonyl oxygen atom of the other adjacent complex molecule, yielding a 2D supramolecular sheet. This sheet is further stabilized by intermolecular N–H⋯Nacetonitrile and N–H⋯Ocarbonate hydrogen bonds and πPyrazine⋯πPyridine interactions. The optical properties of the complex were revealed by UV-vis spectroscopy and spectrofluorimetry in MeOH. It was established that the described complex is emissive upon excitation at 340 nm with a broad band from about 500 nm to 780 nm with a maximum at ∼580 nm, accompanied by a shoulder at ∼620 nm. The CIE-1931 chromaticity coordinates of (0.28, 0.36) fall within the white gamut of the chromaticity diagram. Thus, complex 1 is a single-component white light-emitting phosphor.
Supramolecular coordination polymers, obtained from multidentate N′-benzoylpyrazine-2-carbohydrazonamide and a variety of salts PbX2 (X = Cl− , NO3 − , NO2 − , SCN− ), derived from tetrel and other noncovalent bonds
(Elsevier, 2025-12-25) Mahmoudi, Ghodrat; García Santos, María Isabel; Castiñeiras Campos, Alfonso; Gurbanov, Atash V.; Tutar, Omer Faruk; Panova, Elizaveta V.; Gomila Ribas, Rosa María; Frontera Beccaria, Antonio; Universidade de Santiago de Compostela. Departamento de Química Inorgánica
Four lead(II) complexes, [Pb(HL)Cl2] (1), [Pb(HL)2(NO3)2] (2), [PbL(NO2)] (3) and [PbL(NCS)(H2O)]·H2O (4·H2O), were synthesized from PbX₂ salts and the ligand N′-benzoylpyrazine-2-carbohydrazonamide (HL). Spectroscopic characterization confirmed that complexes 1 and 2 contain the neutral ligand (HL), while 3 and 4·H2O feature its deprotonated form (L). In all structures, the Pb2+ center is N,N′,O-chelated by the ligand. Bond length analysis revealed the longest Pb–N/O bonds in 2 due to coordination of two neutral HL ligands, whereas the deprotonated L− in 3 and 4·H2O resulted in shorter Pb–Nimine and Pb–Ocarbonyl bonds. Secondary Pb⋯X tetrel bonds (X = Cl, N, O, S) form in complexes 1, 3, and 4·H2O due to coordination sphere gaps, leading to supramolecular 1D chains (1, 4·H2O) or a 2D sheet (3). These assemblies are further stabilized by extensive hydrogen bonding and π⋯π stacking interactions. The nature of the tetrel bonds was investigated using MEP surface analysis, dimerization energy calculations, and quantum chemical tools (QTAIM, NCIplot). Electron localization function (ELF) and Laplacian maps differentiated tetrel bonds from primary coordination bonds, and the energy contributions of coexisting tetrel and hydrogen bonds were quantified.

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