Charge-transfer metal-organic frameworks based on CuCN architecture units: Crystal structures, luminescence properties and theoretical investigations

Rong Yi Huang, Chen Xue, Chang Hai Zhu, Zhu Qing Wang, Heng Xu, Xiao Ming Ren

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7 Scopus citations

Abstract

Four CuCN complexes, namely Cu4(CN)4(bix)2 (1), Cu2(CN)2(bmimb) (2), Cu2(CN)2(bmimb) (3) and Cu3(CN)3(bimb) (4), have been prepared via the synchronous redox and self-assembly reaction of Cu(NO3)2, K4[Fe(CN)6] and three structurally related flexible bis(imidazole) ligands, 1,4-bis(imidazol-1-ylmethyl)benzene (bix), 1,4-bis(2-methylimidazol-1-ylmethyl)benzene (bmimb) and 4,4′-bis(1-imidazolyl-1-ylmethyl)biphenyl (bimb) under solvothermal conditions. Although all prepared complexes contain one-dimensional CuCN subchains, they have different structures of 21 helical chain, meso-helical chain, 21-helical chain and zigzag chain for 1, 2, 3 and 4, respectively. Complex 1 presents a three-dimensional framework with (10, 3)-d (utp) topology and exhibits an interesting five-fold interpenetration structure attributed as Class Ia type. Moreover, the five-fold entangled network is turned into an unprecedented three-dimensional binodal (3,6)-connected self-penetrated network via the Cu⋯Cu bond interactions. Most interestingly, 2 and 3 are a pair of isomers, and also generate a three-dimensional uninodal (10, 3) network with ThSi2 and utq topology, respectively, which all display an interesting three-fold interpenetration, and also belong to Class Ia type. Complex 4 displays a distorted two-dimensional (6, 3) topology layer, and further forms a three-dimensional supramolecular structure by weak π⋯π interactions. It is indicated that the organic ligands play a crucial role in the final product structures as well as the solvents. Meanwhile, the complexes present strong green (λmax = 553 (1), 565 (2), 565 (3) and 563 nm (4)) photoluminescence in the solid state at room temperature. The theoretical calculations show that the intense green experimental band can be assigned to a combination of the cyanide group to copper(i) center and cyanide group to cyanide group charge transfer transitions. Additionally, the thermal analyses show that complexes 1-4 possess high thermal stabilities.

Original languageEnglish
Pages (from-to)61200-61209
Number of pages10
JournalRSC Advances
Volume4
Issue number105
DOIs
StatePublished - 2014

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