Semiconductive coordination networks from bismuth(III) bromide and 1,2-bis(methylthio)phenylacetylene-based ligands

This paper reports our initial efforts to integrate phenylacetylene-based conjugate π-electron systems into hybrid semiconductive coordination networks, as part of the larger scheme to fully synergize organic functionalities and electronic properties in crystalline solid-state materials. On the basis of a well-established Pd-catalyzed procedure, ligands of 3,3′,4,4′-tetrakis(methylthio)tolan (L1) and 1,3,5-tris{[3,4- bis(methylthio)phenyl]ethynyl}benzene (L2) were efficiently synthesized in relatively simple procedures. Molecule L1 reacts with BiBr₃ to form a 2D semiconductive coordination network (L1·2BiBr₃), which consists of infinite chains of the BiBr₃ component cross-linked by L1 through the chelation between the 1,2-bis(methylthio) groups and the Bi(III) centers. Molecule L2 reacts with BiBr₃ to from a 1D semiconductive coordination network (L2·2BiBr₃), which features discrete tetrameric Bi₄Br₁₂ units linked by the thioether groups from L2 [only two of the three 1,2-bis(methylthio) groups from each L2 molecule are bonded to the Bi(III) centers]. Diffuse reflectance spectra of both L1·2BiBr₃ and L2·2BiBr₃ feature strong optical absorptions at energy levels significantly lower than those of the corresponding molecular solids (L1 and L2) and BiBr₃, indicating significant electronic interaction between the organic π-electron systems and the BiBr₃ components. Both L1· 2BiBr₃ and L2·2BiBr₃ readily form in high yields and are stable to air, providing advantages for further studies as potentially applicable semiconductive materials. © 2005 American Chemical Society.