posted on 2023-12-15, 23:16authored byHarsh Bhatia, Junjun Guo, Christopher N. Savory, Martyn Rush, David Ian James, Avishek Dey, Charles Chen, Dejan-Krešimir Bučar, Tracey M. Clarke, David O. Scanlon, Robert G. Palgrave, Bob C. Schroeder
Bismuth-based coordination complexes are advantageous
over other
metal complexes, as bismuth is the heaviest nontoxic element with
high spin–orbit coupling and potential optoelectronics applications.
Herein, four bismuth halide-based coordination complexes [Bi2Cl6(phen-thio)2] (1), [Bi2Br6(phen-thio)2] (2), [Bi2I6(phen-thio)2] (3), and
[Bi2I6(phen-Me)2] (4) were synthesized, characterized, and subjected to detailed photophysical
studies. The complexes were characterized by single-crystal X-ray
diffraction, powder X-ray diffraction, and NMR studies. Spectroscopic
analyses of 1–4 in solutions of different
polarities were performed to understand the role of the organic and
inorganic components in determining the ground- and excited-state
properties of the complexes. The photophysical properties of the complexes
were characterized by ground-state absorption, steady-state photoluminescence,
microsecond time-resolved photoluminescence, and absorption spectroscopy.
Periodic density functional theory (DFT) calculations were performed
on the solid-state structures to understand the role of the organic
and inorganic parts of the complexes. The studies showed that changing
the ancillary ligand from chlorine (Cl) and bromine (Br) to iodine
(I) bathochromically shifts the absorption band along with enhancing
the absorption coefficient. Also, changing the halides (Cl, Br to
I) affects the photoluminescent quantum yields of the ligand-centered
(LC) emissive state without markedly affecting the lifetimes. The
combined results confirmed that ground-state properties are strongly
influenced by the inorganic part, and the lower-energy excited state
is LC. This study paves the way to design novel bismuth coordination
complexes for optoelectronic applications by rigorously choosing the
ligands and bismuth salt.