From 7-azaindole to adenine: molecular recognition aspects on mixed-ligand Cu(ii) complexes with deaza-adenine ligands
作者:Alicia Domínguez-Martín、Duane Choquesillo-Lazarte、Jose A. Dobado、Isaac Vidal、Luis Lezama、Josefa María González-Pérez、Alfonso Castiñeiras、Juan Niclós-Gutiérrez
DOI:10.1039/c2dt32191b
日期:——
For a better understanding of the versatile behaviour of adenine as a ligand, a series of 10 ternary copper(II) complexes with deaza-adenine ligands [7-azaindole (1,6,7-trideaza-adenine, H7azain), 4-azabenzimidazole (1,6-dideaza-adenine, H4abim), 5-azabenzimidazole (3,6-dideaza-adenine, H5abim), and 7-deaza-adenine (H7deaA)] have been synthesised and characterised by X-ray diffraction. Likewise, all the compounds studied have been analysed by spectral and thermal methods. The proton tautomers and donor capabilities of the above-mentioned deaza-adenine ligands have been calculated by DFT. We conclude that the increasing presence of N-donors in deaza-adenine ligands favours the proton tautomerism and their versatility as co-ligands. Notably, H7azain consistently uses the same tautomer, H4abim uses two different tautomers but is not protonated by the pentadentate H2EDTA2− ligand, and H(N1)5abim displays the μ2-N7,N9 mode, whereas H(N9)7deaA binds Cu(II) by N3 in cooperation with an intra-molecular N9–H⋯O interaction or using the unprecedented bidentate μ2-N1,N3 bridging mode.
为了更好地理解腺嘌呤作为配体的多样性行为,合成并通过X射线衍射表征了一系列10种三元铜(II)配合物,配体为去氮腺嘌呤类 [7-氮唑吲哚 (1,6,7-三去氮腺嘌呤, H7azain)、4-氮苯并咪唑 (1,6-二去氮腺嘌呤, H4abim)、5-氮苯并咪唑 (3,6-二去氮腺嘌呤, H5abim) 和7-去氮腺嘌呤 (H7deaA)]。同样,所有研究的化合物都通过光谱和热法进行了分析。使用密度泛函理论(DFT)计算了上述去氮腺嘌呤配体的质子互变异构体及其供体能力。我们得出结论,去氮腺嘌呤配体中N-供体的增加有利于质子互变异构现象及其作为共配体的多样性。值得注意的是,H7azain始终使用相同的互变异构体,H4abim使用两种不同的互变异构体,但未被五齿配体H2EDTA2−质子化,而H(N1)5abim显示μ2-N7,N9模式,而H(N9)7deaA通过N3与铜(II)结合,协同作用有内部分子N9–H⋯O相互作用或采用前所未有的二齿μ2-N1,N3桥接模式。