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.