Multi-stimuli Responsive Materials Based On Copper(?)Halide Clusters With Cubane-type Structures

Stimuli-responsive materials have captured the interests of chemists due to their attractive applications in information memory,anti-counterfeiting,photoelectric materials.The transition-metal coordinated compounds with d8/d10 metal centers have been widely used in photoelectric materials,steming from their various types of charge transitions.Among them,copper(?)complexes have received special attraction owing to its low price,lowered toxicity and other advantages.In this system,the behavior of organic groups in response to stimuli-responsive regulation research is still in infancy.Therefore,in this paper,13 Cu4X4 cubane and 4 Cu2X2 rhomboid dimer copper(?)halide-based multi-stimuli-responsive materials were synthesized and their stimuli-responsive were discussed.In detail,for compounds 1-15,three kinds of triphenylphosphine derivatives modified with methyl,methoxy and chlorine(rangring from electron withdrawing to electron donating group)were adopted with substituents locating at different sites.Most of them are classical Cu4X4 cubane and Cu2X2 rhomboid dimer.It is worth mentioning,compound 4 with co-edge double tetrahedron.Besides,compound 7 and 8 are the first copper(?)halide clusters with tetracapped adamantoid geometries.Compound 15 was synthesized connecting two cubanetype by other metal atom.Consequently,LE emission exhibit red shift as temperature drops when substituents on the phenyl groups are electron-withdrawing groups.The reason is that electron-withdrawing groups can increase the chances for XLCT and MLCT.Then,when substituents on the phenyl groups are weak electron-donating groups,the LE emission intensity increases,and the HE emission does not appear as temperature drops.This phenomenon due to weak electron-donating groups filled empty ?*orbitals and transfer XLCT and MLCT to forbidden transition.Besides,when substituents on the phenyl groups are moderate intensity electron-donating groups,LE emission exhibit purple shift and the HE emission intensity increases as temperature drops.This regular provides a way to study luminescent material based on copper.Compound 1 and 2 can be converted to each other,which typical reversible mechanical/thermal/solvent multistimuli-responsive material.The most compounds can be synthesized with simply method,low cost,high yield and good repetition.Among the 18 compounds,compound 1,3,7,10,11 and 17 have excellent stimuli-responsive properties with high stabilities.This work provides theoretical guide for the synthesis and application of stimuli-responsive materials.