Copper cyanide polymers with controllable dimensions modulated by rigid and flexible bis-(imidazole) ligands: synthesis, crystal structure and fluorescence properties

Abstract

A series of cyanide-bridged coordination polymers (CPs), [Cu^I₂(CN)₂(bbi)₃]_n (1, 1D), [{Cu^II(CN)₂}{Cu^I₂(CN)₂}(bimb)₃] (2, 2D), (H₂dip)[Cu^I₄(CN)₆] (3, 3D), [{Cu^I₂(CN)₂}(bix)]_n (4, 3D), and [Cu^I₂(CN)₂(bib)] (5, 2D), (bbi = 4,4′-bis(imidazoly)biphenyl, bimb = 1,4-bis(imidazole-l-yl)butane, dip = 1,5-di(1H-imidazol-l-yl)pentane, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, bib = 1,4-bis(1-imidazolyl)benzene), with controllable dimensions have been prepared under hydrothermal conditions by using different types of rigid and flexible bis-(imidazole) ligands. The characterization of all the polymers has been performed by elemental analyses, infrared spectroscopy (IR), thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. 1 displays two noncovalently-bonded parallel one-dimensional (1D) chains, which are woven to produce a three-dimensional (3D) supramolecular architecture by intermolecular forces. For 2, bimb ligands stabilize the copper(I) and copper(II) mixed-valence states to from a (2,6)-connected two-dimensional (2D) network, which then results in a 3D supramolecular network via intermolecular forces. 3 generates an interesting 3D open framework and the protonated dip ligands as templates and charge compensating agents are encapsulated in the tunnel. In 4, bix ligands act as linkers bridging adjacent 2D networks to generate a 3D coordination framework. 5 is a 2D network structure consisting of [CuCN]_n zigzag chains and bib ligands. Moreover, 1–5 show thermal stabilities and luminescence properties in the solid state at room temperature.