Syntheses, structures and luminescence properties of five coordination polymers based on designed 2,7-bis(4-benzoic acid)-N-(4-benzoic acid) carbazole

Abstract

Herein we report five porous luminescent coordination polymers (CPs), namely, [Zn₃(L₂₇)₂(DMA)₆(H₂O)₄]_n (TCZ-001), [Zn₃(L₂₇)₂(DMA)₆(CH₃CH₂OH)₂]_n (TCZ-002), [Zn₃(L₂₇)₂(DMA)₆(CH₃OH)]_n (TCZ-003), [Cd₃(L₂₇)₂(DMA)₆(H₂O)₂]_n (TCZ-004), and [Cd₉(L₂₇)₆DMA₁₃(4,4′-BPY)₂(OH)₂(H₂O)_13.5]_n (TCZ-005) [H₃L₂₇ = 2,7-bis(4-benzoic acid)-N-(4-benzoic acid) carbazole, DMA = N,N-dimethylacetamide, 4,4′-BPY = 4,4′-bipyridine, TCZ = “T”-shape carbazole-based polymers, L₂₇ = fully deprotonated H₃L₂₇³⁻ ligand]. All of the five CPs were assembled from a novel luminescent carbazole-based ligand. X-ray crystallography showed that TCZ-001 is a 3-connected one-dimensional (1D) chain structure with a {4²·6} topology. TCZ-002 possesses a 3,6-connected three-dimensional (3D) framework with a point symbol of {4²·6}₂{4⁴·6²·8⁷·10²}. TCZ-003 displays a 3,6-connected two-dimensional 2D network with a Schläfli symbol of {4¹¹·6⁴}·{4³}₂, which is a new topology. TCZ-004 features a 3,6-connected 2D net with a {4³}₂·{4⁶·6⁶·8³} topology. In TCZ-005, the structure can be classified into two groups: one of the two groups is a 3-connected 1D chain structure with a {4²·6} topology, similar to TCZ-001; the other one possesses a 3,3,3,4-connected network with a Schläfli symbol of {4²·6³·8}{4²·6}₃. The structure of TCZ-005 could be described as an SP 1-periodic net (4,4)(0,2) in the 1D_2D.ttd database. TCZ-001, TCZ-003 and TCZ-004 show a remarkable response to the Ni²⁺ concentration in DMA, H₂O or EtOH. Some of Zn²⁺ ions were replaced by Ni²⁺ ions and the rate of the transmetalation depended on the concentration of Ni²⁺ ions. Also, changing part of the metal node would transform the colour of emitted light. Additionally, the colour of the luminescence displays a linear correlation with the Ni²⁺ concentration range from 0.005 to 0.35 M (mol L⁻¹). Besides selective sensing of Ni²⁺, TCZ-004 can also be utilized to detect Eu³⁺ in DMA solution. Thus, several potential sensory probe materials for Ni²⁺ and Eu³⁺ detection in DMA solution have been obtained.