TITLE:
A Theoretical Study of Tris-(o-benzoquinonediimine)-First-Row Divalent Transition Metal Complexes
AUTHORS:
Mohammad Abdul Matin, Samiran Bhattacharjee, Anwar Hossain
KEYWORDS:
DFT, o-phenylenediamine, o-benzoquinodiimine, First-Row Divalent Transition Metals, Time Dependent–DFT, Coordination Complexes
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.13 No.2,
April
21,
2023
ABSTRACT: The
ligand o-phenylenediamine (opda) and its oxidized
form, o-benzoquinonediimine (bqdi), act as a
fascinating candidate coordinating toward transition metal ions leading to the photochemical hydrogen production in
absence of photosensitizers. Herein, we report the systematic study of the
interaction between the oxidized form bqdi ligand, tris-(o-benzoquinonediimine) with divalent first-row
transition metal series using DFT calculations. The lowest energy structures,
bond length, binding energies, frontier molecular orbital analysis, natural
bond orbitals, and global reactivity descriptor were calculated using
B3LYP/6-311G(d,P) level of theory. The time dependent-DFT at
the CAM-B3LYP/6-311+G(d,p) level of theory was applied to determine the
electronic structures and the optical spectra. The theoretical binding trend of
the divalent first-row transition metal series is decreasing as follows: Cu
>Ti > V > Co > Ni > Fe > Cr > Zn >Mn. Among them, the
binding potency of iron (II) by the bqdi ligand was not predominantly sturdy as
compared to other first-row divalent transition metal ions. The origin of
strong coordination with Fe(II) is attributed to its extra capability to induce
covalent coordination of bqdi ligands. The complex exhibited two strong peaks
at 370 nm and 452 nm, due to the HOMO-3 to LUMO+1 and HOMO-1 to LUMO
transitions, respectively. Natural bond orbital analysis showed that the major
interaction happens between the N lone pair electrons of the ligand with an
anti-bonding orbital of metal ions, in which Ti showed the highest interaction energy than other metal ions. The present
systemic DFT study of bqdi ligands with the first-row transition metals
strongly encourages the future establishment of photochemical hydrogen production in absence of photosensitizers.