The Synthesis And Characterization Of New Photochromic Iodoargentate/Iodocuprate Hybrids

Organic-inorganic photochromic hybrid materials have drawn increasing attentions in the field of functional materials due to their versatile and tunable compositions,structures,and intriguing properties.Especially,photochromic hybrids based on intermolecular electron transfer(ET)between donor and acceptor are extensively studied for their excellent stimuli-response ability and visual detectability.However,the effect of matching relationship of donor-acceptor on internal electronic behavior and photochromic property has not been fully explored because of the limited types of electron acceptors and donors employed in these materials.Accordingly,the synthesis of new photochromic hybrid materials through choosing appropriate electron acceptors and donors would be great significance to enrich the type of photochromic materials and optimize chromic properties.In this paper,by choosing nicotinohydrazide derivative dications as structural directing agents and electron acceptors,seven iodoargentate/iodocuprate hybrids have been obtained via solvent evaporation and solvothermal reaction,six of which exhibit apparent photochromism.Their structures and properties have beencharacterized by single-crystal/power X-ray diffraction,EA,IR,EPR,UV-vis diffuse reflectance spectra,and so on.The structure-directing role of organic dications,photochromic mechanism,struction-function relationship,as well as the effect of donor-acceptor matching rule on internal electronic behavior and photochromic property are investigated.The main conclusions are listed as follow: Firstly,the photochromism of these iodometallates can be attributed to the generation of colored organic radicals arising from intermolecular ET between the electron donors and acceptors.Secondly,the formation of mixed valence copper has a promoting effect on ET process and photochromism.Lastly,the substituent position of cations,dimensionality of anionic frameworks and nature of metal ions have influence on the photoresponse rate and photocoloration contrast.This study indicates that weaker electron acceptors(HNH2+and MNH2+)can match well with weaker electron donors(iodometallate frameworks)to undergo intermolecular ET and photochromism,which is contrary to the matching rule found in strongly electron-accepting viologen-based photochromic hybrids.