Unexpected Formation of a Doubly Bridged Cyclo-1,2-dithian 1D Coordination Cu2I2-Containing Luminescent Polymer

Abstract  

CuI reacts instantaneously with butanedithiol in MeCN solution to form a sparingly soluble and thermally stable colorless polymeric material 1 of composition [(Cu₂I₂){HS(CH₂)₄SH}] _n . Raman and IR spectroscopy confirm the presence of Cu(I) bound S–H functions. Furthermore, small amounts of the yellow compound [{Cu(μ₂-I)₂Cu}(C₄H₈S₂)₂] _n 2 co-crystallize after several days. If the reaction mixture is exposed to air, polymeric 2 is isolated as the main product. An X-ray diffraction study reveals that 1D polymer 2 is assembled by rhomboid Cu(μ₂-I)₂Cu clusters (d Cu···Cu 2.6843(18) ?), which are linked through the S-atoms of six-membered 1,2-dithian heterocycles, thus generating an infinite ribbon. The low-frequency region in the Raman spectra show a striking similarity suggesting that polymers 1 and 2 bear the same cluster rhomboid Cu(μ₂-I)₂Cu clusters. The photophysics and luminescence properties of 2 have been studied experimentally and by means of DFT/TDDFT calculations.