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Thermochromic, Solvatochromic, and Piezochromic Cd(II) and Zn(II) Coordination Polymers: Detection of Small Molecules by Luminescence Switching from Blue to Green

Research paper by Avishek Dey, Abhijit Garai, Venkatesh Gude, Kumar Biradha

Indexed on: 07 Sep '18Published on: 27 Aug '18Published in: Crystal Growth & Design



Abstract

The Cd(II) and Zn(II) two-dimensional porous and multichromic coordination polymers have been synthesized which consist of an alternate (6,3) brick wall and (4,4) rectangular grid network such that there exist continuous channels. These materials are also found to exhibit multichromism properties such as solvatochromism, thermochromism, and piezochromism when subjected to various external stimuli.Two novel Cd(II) and Zn(II) based multichromic coordination polymers (CPs) containing 2,4,5-tri(4-pyridyl)-imidazole, L, with general formulas {[Cd2L4(SO4)(H2O)]·(SO4)·21H2O}n, 1, and {[Zn2L4(SO4)(H2O)2]·2(MeOSO3)·25H2O}n, 2, have been synthesized which consist of two-dimensional layered structures with continuous channels. These CPs are found to exhibit instant and reversible solvatochromic properties via visual color change in the presence of various solvent molecules such as DMF, DMA, CH3CN, CH3COCH3, DMSO, and Et3N as well as quick response for the absorption/detection of small molecules such as formaldehyde and acetaldehyde compared to higher aldehydes. The thermochromic and solvatochromic properties are associated with a color change from blue to green under UV light with significant changes in their emission properties and lifetimes. Further, piezochromic properties are associated with color change from blue to cyan under UV. These materials were also found to exhibit greater preference for adsorption of water vapor (200–300 cc/g) over N2 and CO2 gases and also anionic dye sorption such as Congo red from aqueous solution.

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