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 pi-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 pi-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.