Benzimidazole and its derivatives are molecules that have diverse biological properties, therefore we synthesized and studied a new benzimidazole to understand their physical/chemical properties. The compound was obtained through a new synthetic route, using graphite oxide, in the absence of solvent, with crystalline packaging supported by C-H…N and C-H…π interactions. According to the frontier molecular orbitals, the compound is kinetically stable while the molecular electrostatic potential map confirms the site of molecular interactions involving nitrogen atoms and the π-system. This comprehensive study on synthesis, structural description and theoretical calculations can support ongoing studies in pharmaceutical science.

Herein, we present three new binuclear copper(II) complexes containing different polycyclic aromatic hydrocarbons, able to catalyze the oxidation of 3,5-di-tert-butylcathecol, a model substrate for catechol oxidase. The ligands and complexes were successful characterized in solid and solution states. The structure of C1 was determined by X-ray crystallography and it contains a [CuII2(L1-µ-phenoxo)(OAc)(H2O)2] unit, with two coppers in a pyramidal square geometry and a large distance of 3.715 Å between the copper(II) centers. All complexes (C1, C2 and C3) were found to be effective catalysts in the oxidation of 3,5-di-tert-butylcathecol to its quinone and C1 provided the highest catalytic constants at the three pH values studied. In addition to their potential use as a biomimetic catalyst in catechol oxidation, the interaction of these complexes with deoxyribonucleic acid from calf thymus (CT-DNA) was also studied, and C3 showed the greatest affinity with nucleic acids.

Currently, there is great interest in the study of water-soluble metal compounds capable of releasing carbon monoxide, due to their potential therapeutic use. This paper reports the synthesis, spectroscopic characteristics and CO release properties of three water-soluble manganese(I) carbonyl compounds [Mn(aaz)(CO)3]Br (1; where aaz = 6-amino-6-methylperhydro-1,4-diazepine), [Mn(Me2aaz)(CO)3]Br (2; where Me2aaz = 6-amino-1,4,6-trimethyl-1,4-diazacycloheptane) and [Mn(tacn)(CO)3]Br (3; where tacn = 1,4,7-triazacyclononane), that can act as photoCORMs (where CORM is carbon monoxide-releasing molecule). The main aim was to propose a mechanism for the CO release. Compounds 1-3 are capable of releasing carbon monoxide when exposed to light (λ385 and λ410) and thus, act as photoCORMs. The formation of a biscarbonyl intermediate was identified during the photo-release process at λ385 and the quantum yields and rates of CO release were determined. The proposed CO release mechanisms involve two steps, where photo and redox processes take place, and compounds 1 and 2 exhibit a slightly different mechanism from compound 3. A good understanding of the CO photo-release mechanism is very important with regard to the development of more efficient compounds, particularly those intended for medical applications.

This paper describes the use of digital imaging acquired from a conventional desktop scanner for characterization of newly synthesized amino-nitroquinoxaline dyes. The synthetic protocol was based on reactions of building block 2,3-dichloro-6,7-dinitroquinoxaline with aliphatic amines and experiments based on image analysis were carried out with compounds in solution (96-microwell plates) and/or adsorbed on silica (thin-layer chromatography (TLC) plates). Three main goals were achieved: firstly, compounds 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline and 6,7-dinitro-2,3-dipyrrolidinoquinoxaline had their concentration predicted in dimethyl sulfoxide (DMSO) solution, as a mixture. Secondly, TLC studies were performed to build a kinetic profile in attempt to monitor reaction involving conversion of 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline into 6,7-dinitro-2,3-dipyrrolidinoquinoxaline. Lastly, image analysis and UV-Vis spectroscopy were applied to study the interaction of 2,3-di-n-butylamino-6,7-dinitroquinoxaline with hydroxide anion in DMSO. These approaches based on digital image characterization were successfully implemented in qualitative and quantitative analysis of organic dyes.

The synthesis of five quinolines 8-octyloxy-4-[4-(octyloxy)phenyl]quinoline and 6-alkoxy- 2-(4-alkoxyphenyl)-4-[(4-octyloxy)aryl]quinolines are described by three-component coupling reaction mediated by Lewis acid FeCl3 and Yb(OTf)3. 4-n-octyloxybenzaldehyde, anisaldehyde, 4-n-octyloxyaniline p-anisidine, and 1-ethynyl-4-heptyloxybenzene, 1-ethynyl-4-octyloxybenzene and 2-ethynyl-6-heptyloxynaphthalene are the reagents in this protocol. A Yb3+ catalyst resulted in higher yields of quinolines than Fe3+. Polarizing optical microscopy (POM) revealed that none of the quinolines were liquid crystals, even the more anisotropic. UV-Vis measurements of one of the quinolines in polar solvent show two absorption bands at 280 and 350 nm related to π,π* and n,π* transitions. No changes were observed to lower-energy absorption band (ε < 104 mol L-1 cm-1) related to n,π* transition. A laser flash photolysis study for one of the quinolines relates a main transient band at 450 nm with a lifetime of 2.6 µs in ethanol, which is completely quenched in the presence of oxygen. This transient band was assigned to triplet-triplet absorption of one of the quinolines, which is semi-oxidised in the presence of phenol. Radiative rate constants have been determined along singlet and triplet excited state energies (3.39 and 3.10 eV, respectively). The chemical structure of one of the quinolines was also unequivocally confirmed by single-crystal X-ray analysis.

trans-Desidrocrotonina (t-DCTN), um bioditerpeno do tipo 19-nor-clerodano isolado de Croton cajucara Benth, representa um dos clerodanos da atualidade com maiores índices de investigações científicas. Neste trabalho, uma nova abordagem unindo dados de difração de raios X, dados de ressonância magnética nuclear (NMR) e dados teóricos foi aplicada para a completa caracterização da t-DCTN. Para tanto, a geometria de t-DCTN foi reavaliada por difração de raios X e NMR de ¹H e 13C e foi comparada com os dados teóricos obtidos por B3LYP/6-311G++(d,p). A subsequente avaliação dos valores teóricos e experimentais de deslocamentos químicos de NMR e constantes de acoplamento spin-spin apresentou correlações muito boas entre propriedades magnéticas teóricas e experimentais. Adicionalmente, os índices de deslocalização entre átomos de hidrogênio, d(H,H'), correlacionaram bem com os dados experimentais e calculados de constante de acoplamento. Uma análise topológica complementar utilizando a teoria quântica de átomos em moléculas (QTAIM) mostrou interações intramoleculares para t-DCTN.

trans-Dehydrocrotonin (t-DCTN) a bioactive 19-nor-diterpenoid clerodane type isolated from Croton cajucara Benth, is one of the most investigated clerodane in the current literature. In this work, a new approach joining X-ray diffraction data, nuclear magnetic resonance (NMR) data and theoretical calculations was applied to the thorough characterization of t-DCTN. For that, the geometry of t-DCTN was reevaluated by X-ray diffraction as well as ¹H and 13C NMR data, whose geometrical parameters where compared to those obtained from B3LYP/6-311G++(d,p) level of theory. From the evaluation of both calculated and experimental values of ¹H and 13C NMR chemical shifts and spin-spin coupling constants, it was found very good correlations between theoretical and experimental magnetic properties of t-DCTN. Additionally, the delocalization indexes between hydrogen atoms correlated accurately with theoretical and experimental spin-spin coupling constants. An additional topological analysis from quantum theory of atoms in molecules (QTAIM) showed intramolecular interactions for t-DCTN.

O novo diterpeno clerodano 3-oxo-12-epibarbascoato de metila foi isolado das cascas do caule de Croton urucurana, juntamente com o diterpeno conhecido como 12-epibarbascoato de metila. As estruturas destes compostos foram elucidadas através de técnicas espectroscópicas e por comparação com dados da literatura. A obtenção de cristais possibilitou a análise cristalográfica da difração de raios X dos diterpenos, confirmando assim as estruturas propostas.

The new clerodane diterpene methyl 3-oxo-12-epibarbascoate was isolated from the stem barks of Croton urucurana together with the known diterpene methyl 12-epibarbascoate. The structures of these compounds were elucidated by spectroscopic techniques and comparison with the literature data. The obtainment of crystals allowed the crystallographic analysis of X-ray diffraction of diterpenes, thus confirming the proposed structures.

Neste artigo são apresentadas a síntese e a caracterização de dois compostos binucleares de ferro, os quais contêm uma ponte μ-oxo. Os compostos [(SO4)(L5)Fe(μ-O)Fe(L5)(SO4 )]•6H2O, 1, e [Cl(L5)Fe(μ-O)Fe(L5)Cl]Cl2• 2H2O, 2, foram obtidos nas reações entre 1-(bis-piridin-2-ilmetil-amino)-3-cloropropan-2-ol (L5) e os sais FeSO4•7H2 O e FeCl3•6H2 O, respectivamente. Os espectros eletrônicos dos complexos apresentam absorções somente na região do ultravioleta, sendo que a análise eletroquímica revelou que, após a formação da espécie FeIII FeII, a unidade binuclear do composto 1 é mais estável do que a do composto 2. Os ligantes monodentados (sulfato e cloreto) exercem influência sobre os parâmetros Mössbauer determinados para 1 e 2, particularmente sobre os desdobramentos de quadrupolo. Os compostos foram empregados como catalisadores em reações de oxidação do cicloexano, usando H2O2 e t-BuOOH como oxidantes em uma razão substrato:oxidante:catalisador de 1000:1000:1. Os resultados indicam que o composto 2 é um catalisador mais eficiente que o composto 1.

We report herein the synthesis and characterization of two dinuclear μ-oxo iron compounds obtained through the reactions of FeSO4•7H2 O and FeCl3•6H2 O with 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol (L5), which resulted in the compounds [(SO4)(L5)Fe(μ-O)Fe(L5)(SO4 )]•6H2O, 1, and [Cl(L5)Fe(μ-O)Fe(L5)Cl]Cl2• 2H2O, 2. The electronic spectra of both compounds show absorption bands only in the UV range. The electrochemical analysis showed that the dinuclear unit is more stable under reduction in compound 1 than in compound 2, while the Mössbauer spectroscopy revealed that the monodentate ligands (sulfate and chloride) have a significant influence on the Mössbauer parameters determined for 1 and 2, particularly on the quadrupole splitting values. Both compounds were studied as catalysts in reactions of cyclohexane oxidation, using H2O2 and t-BuOOH as oxidants, in a substrate:oxidant:catalyst ratio of 1000:1000:1. Cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide, t-butyl cyclohexyl peroxide and adipic acid were formed during the process. The experiments revealed that compound 2 is, in general, more active than compound 1 in promoting cyclohexane oxidation.

Os estudos sobre enzimas têm mostrado que existe uma relação clara entre a evolução enzimática e a propriedade de promiscuidade catalítica que elas podem apresentar. Com isto, o desenvolvimento de sistemas biomiméticos capazes de atuar de modo promíscuo, de forma similar a algumas enzimas, mostrou-se um novo desafio para os químicos bioinorgânicos. Neste trabalho, reportamos a estrutura de raios X e os estudos em solução e de promiscuidade catalítica do complexo [(bpbpmp)FeIII(µ-OAc)2FeII](ClO4), (1), contendo o ligante binucleante não-simétrico 2-{[(2-hidroxibenzil)(2-piridilmetil)aminometil]-4-metil-6-[bis(2-piridilmetil)aminometil]}fenol (H2bpbpmp). Estudos de titulações potenciométrica e espectrofotométrica e cinéticos mostraram que esse composto de coordenação gera espécies ativas capazes de clivar o dsDNA (DNA de fita dupla) hidroliticamente, com um aumento de 1,9×10(8) na taxa de reação em comparação com a reação não catalisada, e capazes de oxidar o 3,5-di-terc-butilcatecol (3,5-dtbc), com k cat = 1,16 × 10-2 s-1 e K M = 7,1×10-4 mol L-1. Assim, o complexo 1 apresenta atividades de hidrolase e oxidoredutase, sendo um interessante modelo sintético para estudos de promiscuidade catalítica.

Catalytic promiscuity has emerged as an important property of many enzymes since the relationship of this property to enzymatic evolution became clear. Simultaneously, the development of suitable biomimetic catalytic systems capable of mimicking the promiscuous catalytic properties of such enzymes represents a new challenge for bioinorganic chemists. In this paper we report on the X-ray structure, the solution studies and the promiscuous catalytic activity of the mixed-valence complex [(bpbpmp)FeIII(µ-OAc)2FeII](ClO4), (1), containing the unsymmetrical dinucleating ligand 2-{[(2-hydroxybenzyl)(2-pyridylmethyl)aminomethyl]-4-methyl-6-[bis(2-pyridylmethyl)aminomethyl]}phenol (H2bpbpmp). Potentiometric and spectrophotometric titrations and kinetics studies showed that this coordination compound generates active species that promote hydrolytic cleavage of double strand DNA (dsDNA), with a rate enhancement of 1.9×10(8) over the non-catalyzed reaction, as well as promote oxidation of 3,5-di-tert-butylcatechol (3,5-dtbc), with k cat = 1.16 × 10-2 s-1 and K M = 7.1×10-4 mol L-1. Thus, complex 1 shows both hydrolase and oxidoreductase activities and can be regarded as a man-made model for studying catalytic promiscuity.

1,2-dichloro-4,5-dinitrobenzene (DCDNB) reacts with primary and secondary amines, in acetonitrile, at room temperature, to give a monosubstituted nitro product with a yield of 85 to 95%. The chloro-nitro-disubstituted product is formed with excess amine under reflux. Piperidine, pyrroline, dimethylamine and methylamine were the most reactive reagents in both mono- and disubstitution.

Reportamos aqui a síntese e caracterização do ligante hexadentado H2L (N,N',N,N'-bis[(2-hidroxi-3,5-di-terc -butilbenzil)(2-piridilmetil)]etilenodiamino), como derivado adicional do bem conhecido pré-ligante H2bbpen, e que contém dois grupos fenolatos e dois grupos piridínicos conectados à unidade etilenodiamina. Os grupos fenolatos no pré-ligante H2L estão adequadamente protegidos por grupos substituintes volumosos (terc-butil) nas posições orto- e para-, a partir dos quais complexos contendo radicais fenoxil estáveis podem ser obtidos. Assim, sintetizamos quatro novos complexos mononucleares com MnIII, GaIII, InIII e FeIII, que através de oxidação eletroquímica produzem espécies fenoxil mono- ou di-oxidadas em solução. Estas espécies radicalares foram caracterizadas por espectroscopia UV-Vis e Ressonância Paramagnética Eletrônica e estudos eletroquímicos. Como esperado, no caso dos complexos de GaIII, InIII e FeIII, nenhum processo de oxidação centrado no metal foi observado. Entretanto, o complexo de manganês sofre processos de oxidação centrados tanto no metal quanto no ligante e conseqüentemente um complexo MnIV-radical fenoxil pode ser gerado em solução. As estruturas dos complexos [MnIII(L)]+ e [GaIII(L)]+ foram determinadas por análises de cristalografia de raios X, revelando complexos monocatiônicos com geometrias octaédricas distorcidas.

Reported herein are the synthesis and characterization of the hexadentate H2L pro-ligand (N,N',N,N'-bis[(2-hydroxy-3,5-di-tert -butylbenzyl)(2-pyridylmethyl)]ethylenediamine), as a further derivative of the well known pro-ligand H2bbpen which contains two phenolate and two pyridyl pendant arms. The phenolate groups in H2L are suitably protected by bulky substituents (tert-butyl) in the ortho- and para- positions, from which stable phenoxyl radical complexes can be formed. Thus, we have synthesized four new mononuclear complexes with MnIII, GaIII, InIII and FeIII which through electrochemical oxidation generate one- and two-electron oxidized phenoxyl species in solution. These radical species were characterized by UV-Vis, Electronic Paramagnetic Resonance and electrochemical studies. As expected, in the case of the GaIII, InIII and FeIII complexes no metal-centered oxidation was observed. However, the manganese complex undergoes metal- and ligand-centered oxidation processes and therefore a phenoxyl radical-MnIV complex can be generated in solution. The crystal structures of the [MnIII(L)]+ and [GaIII(L)]+ complexes were determined by X-ray crystallographic analyses revealing monocationic complexes with distorted octahedral geometries.

A reação entre Fe(ClO4)3.nH2O e N,N'-bis[(2-hidroxibenzil)-N,N' -bis(1-metilimidazol-2-il-metil)]etilenodiamina (H2bbimen) resulta na formação de dois isômeros geométricos, A e B, do cátion complexo [Fe(bbimen)]+, os quais foram isolados e caracterizados por espectroscopia na região do infravermelho e UV-visível, espectrometria de massas, medidas de condutividade molar, voltametria cíclica, espectroeletroquímica e espectroscopia de ressonância paramagnética eletrônica (RPE). A geometria de um desses isômeros foi claramente demonstrada por análise cristalográfica de raios X de monocristal. O composto cristaliza no sistema monoclínico, grupo espacial P2(1)/c, a = 14,104 (3), b = 15,626 (3), c = 13,291 (3) Å, beta = 98,07 (3)º, Z = 4, R1 = 6,35% e wR2 = 20,57%. As propriedades eletroquímicas do cátion [Fe(bbimen)]+ (-0,58 V versus NHE) são bastante similares às das transferrinas (-0,52 V versus NHE), indicando que o complexo é um bom modelo para as propriedades redox daquelas metaloenzimas. A espectroscopia de RPE foi a única técnica espectroscópica capaz de diferenciar os dois isômeros isolados (A e B). Os estudos de RPE revelaram que o isômero A trata-se de um complexo de FeIII spin alto distorcido rombicamente (E/D <FONT FACE=Symbol>@</FONT> 0,33) e apresenta um espectro caracterizado por uma linha estreita em g1 <FONT FACE=Symbol>@</FONT> 4,1 e outra larga em g2 <FONT FACE=Symbol>@</FONT> 9,0. O espectro de RPE do isômero B apresenta, além das linhas em g1 <FONT FACE=Symbol>@</FONT> 4,2 e em g2 <FONT FACE=Symbol>@</FONT> 9,0, um conjunto de linhas em g1 <FONT FACE=Symbol>@</FONT> 3,0, g2 <FONT FACE=Symbol>@</FONT> 3,6 e g3 <FONT FACE=Symbol>@</FONT> 5,1, que têm sido atribuídas a complexos de FeIII com simetria tendendo à axial (E/D <FONT FACE=Symbol>@</FONT> 0,22). Estudos teóricos empregando cálculos semi-empíricos, combinados com os dados de RPE, foram essenciais para a atribuição das estruturas geométricas dos isômeros A e B.

The reaction of Fe(ClO4)3.nH2O with N,N'-bis[(2-hydroxybenzyl)-N,N' -bis(1-methylimidazole-2-yl-methyl)]ethylenediamine (H2bbimen) affords two geometric isomers, A and B, of the complex cation [Fe(bbimen)]+, which were fully characterized by IR and UV-visible spectroscopies, ESI mass spectrometry, molar conductivity measurements, cyclic voltammetry, spectroelectrochemistry and EPR spectroscopy. The geometry of one of these isomers has been clearly demonstrated through X-ray crystallographic analysis. It crystallizes in the monoclinic system, space group P2(1)/c, a = 14.104 (3), b = 15.626 (3), c = 13.291 (3) Å, beta = 98.07 (3)º, Z = 4, R1 = 6.35% and wR2 = 20.57%. The electrochemical properties of [Fe(bbimen)]+ (-0.58 V versus NHE) are quite similar to those of transferrins (-0.52 V versus NHE) and indicate that it is a good model for the redox potential of these metalloenzymes. EPR spectroscopy was the only spectroscopic technique able to differentiate the isolated isomers A and B. EPR studies revealed that isomer A is better described as a rhombically distorted (E/D <FONT FACE=Symbol>@</FONT> 0.33) high-spin FeIII complex (g1 <FONT FACE=Symbol>@</FONT> 4.1 with a shoulder at g2 <FONT FACE=Symbol>@</FONT> 9.0), while the spectrum of B has a set of lines at g1 <FONT FACE=Symbol>@</FONT> 3.0, g2 <FONT FACE=Symbol>@</FONT> 3.6 and g3 <FONT FACE=Symbol>@</FONT> 5.1, in addition to the line at g1 <FONT FACE=Symbol>@</FONT> 4.2 and a shoulder at g2 <FONT FACE=Symbol>@</FONT> 9.0, which have been ascribed to FeIII complexes in axial symmetry (E/D <FONT FACE=Symbol>@</FONT> 0.22). Semi-empirical theoretical studies, combined with EPR data, were essential to the proposition of the geometric structures of A and B.

O complexo [Fe2III(BPClNOL)2(SO4)] 3 foi sintetizado pela reação do pré-ligante N-(2-hidroxibenzil)-N-(2-metilpiridil)[(3-cloro)(2-hidroxi)]propilamina (H2BPClNOL) com FeSO4.7H2O. O composto oxidado apresenta absorção máxima em 519 nm (épsilon = 1,40X10³ dm³ mol-1 cm-1) e a espécie de valência mista absorve em 439 nm (épsilon = 9,8X10² dm³ mol-1 cm-1). O processo de redução da espécie oxidada ocorre em -0,843 V vs. Fc/Fc+. A espectroscopia Mössbauer confirmou que o composto 3 possui átomos de Fe3+, spin alto. Medidas magnéticas mostram que a unidade binuclear apresenta acoplamento antiferromagnético, J/kB = - 15 K (J =-10,4 cm-1). O complexo [Fe2III(BPClNOL)2(SO4)] 3 é o terceiro integrante de uma família de compostos binucleares de ferro sintetizados com o ligante H2BPClNOL ([Fe2III(BPClNOL)2 (OAc)]+ 1, [Fe2III(BPClNOL)2(H2O) 2]2+ 2). A comparação das propriedades físico-químicas dos complexos indica que o número de grupos pontes, assim como a natureza dos mesmos, apresentam significativas influências sobre o espectro eletrônico e as propriedades eletroquímicas dos referidos complexos.

Complex [Fe2III(BPClNOL)2(SO4)] 3 was synthesized through the reaction of the pro-ligand N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine (H2BPClNOL) and FeSO4.7H2O. The maximum absorption for the oxidized compound was at 519 nm (epsilon = 1.40X10³ dm³ mol-1 cm-1) while that of the mixed-valence compound was at 439 nm (epsilon = 9.8X10² dm³ mol-1 cm-1). The redox process to transform the oxidized compound to the mixed-valence form occurs at E1/2 = -0.843 V vs. Fc/Fc+. The Mössbauer spectrum confirms the presence of FeIII high spin ions and the magnetic studies reveal a weak antiferromagnetically coupled dimer, J/kB = - 15 K ( J = -10.4 cm-1). Complex 3 is the third of a family of dinuclear iron compounds synthesized with the H2BPClNOL ligand ([Fe2III(BPClNOL)2 (OAc)]+ 1, [Fe2III(BPClNOL)2(H2O) 2]2+ 2). Analysis of the physicochemical properties of these complexes allowed us to infer that the number and kind of bridging groups have a significant influence on their electrochemical and UV-Vis properties.

O objetivo deste trabalho é apresentar a síntese, estrutura cristalina, atividade eletroquímica, propriedades espectroscópicas (IV-TF e UV-Vis) e atividade catalítica frente à oxidação do benzeno do novo complexo mononuclear de cobre(II) [Cu(BTMEA)2Cl]Cl, (1) (BTMEA: bis(2-tienilmetil)-1,2-etilenodiamina). A reação entre BTMEA e [Cu(OH2)2]Cl2, em metanol, resultou em 1, o qual cristaliza como um cristal irregular azul, no grupo espacial Pnna, com a = 20,101(3), b = 12,094(6), c = 12,741(2) Å, V = 3097,4(17) ų, Z = 4. Em 1, o íon cobre está pentacoordenado, mostrando uma geometria de pirâmide de base quadrada distorcida. Complexo 1 apresenta dois processos redox irreverssíveis a - 0,35 V e 0,456 V versus NHE, os quais são atribuídos ao processo redox CuII/CuI e a uma reação acoplada envolvendo o ligante cloreto. A atividade catalítica de 1 foi avaliada através da reação de oxidação do benzeno, usando peróxido de hidrogênio como oxidante. Os produtos da reação (fenol e p-benzoquinona) foram identificados por cromatografia gasosa.

The aim of this work is to present the synthesis, crystal structure, electrochemical behavior, spectroscopic properties (FT-IR and UV-Vis) and catalytic activity toward benzene oxidation of a new mononuclear copper(II) complex [Cu(BMTEA)2Cl]Cl, (1) (BTMEA: bis(2-thienylmethyl)-1,2-ethylenediamine). The reaction between BTMEA and [Cu(OH2)2]Cl2, in methanol, resulted in 1, which crystallizes as an irregular blue crystal, space group Pnna, with a = 20.101(3), b = 12.094(6), c = 12.741(2) Å, V = 3097.4(17) ų, Z = 4. In 1, the copper ion is pentacoordinated, showing a distorted square pyramidal geometry. Complex 1 shows two irreversible redox processes at -0.35 V and at 0.456 V versus NHE, which are associated with the CuII/CuI redox couple and with a coupled reaction involving the chloride ligand. The catalytic activity of 1 was evaluated through benzene oxidation reaction, using hydrogen peroxide as oxidant. Reaction products (phenol and p-benzoquinone) were identified by gas chromatography.

Apresentamos neste trabalho a síntese, estrutura cristalina e as propriedades espectrais de ¹H NMR do complexo mononuclear [ZnII(L-Br)].2H2O o qual contém em sua primeira esfera de coordenação, o ligante hexadentado H2L-Br (H2L-Br = N,N'-bis-(5- bromo-2-hidróxibenzil)- N,N'-bis-(piridin-2-ilmetil)-1,2-etanodiamina). Cálculos teóricos utilizando DFT mostram boa correlação entre os parâmetros calculados e aqueles obtidos através de cristalografia de raios X em monocristais e revelam que somente os grupos fenolatos do ligante H2L-Br participam na formação do HOMO, enquanto somente os anéis piridínicos contribuem para a formação do LUMO.

We describe herein the synthesis, crystal structure and ¹H NMR properties of the mononuclear [ZnII(L-Br)].2H2O complex containing the hexadentate H2L-Br ligand (H2L-Br = N,N'-bis-(5-bromo-2-hydroxybenzyl)-N,N '-bis-(pyridin-2-ylmethyl)-ethane-1,2-diamine). DFT calculations demonstrate very good agreement between parameters calculated and those determined by X-ray crystallography, and reveal that only the phenolate groups of the H2L-Br ligand participate in the formation of the HOMO, while only one of the pyridine rings contributes to the LUMO formation.