Two bis-tridentate Os(II) compounds
based on a heteroditopic terpyridine–bipyridine-type
ligand were synthesized, and their photophysical properties were thoroughly
studied. The compounds exhibit strong spin-allowed
1
MLCT
bands in the visible domain (489–521 nm) as well as weak
1
GS to
3
MLCT bands within the 668–815 nm
domain. The compounds display strong luminescence from the
3
MLCT state in the near-infrared domain (728–780 nm) at room
temperature having lifetimes in the range of 20.0–171.0 ns.
After coordination of [Os(tpy-PhCH
3
/H
2
pbbzim)
2
]
2+
unit to the terpyridine site of tpy-Hbzim-dipy,
the complexes offer vacant pyridine–imidazole motifs for interacting
with cationic and anionic guests. Consequently, photophysical properties
of the compounds were tuned to a great extent upon interaction with
selected cations, anions, pH, as well as protons. Anion-induced alteration
of the ground- and excited-state properties of the compound lead to
recognition of specific anions in solution. Significant change in
the optical spectral behaviors as well as switching of emission spectral
properties of the compounds was done in the NIR region upon treating
with anions, cations, protons, and solvents (dichloromethane, acetonitrile,
methanol, dimethylsulfoxide, and water). Moreover, the optical outputs
in response to external stimuli were used to demonstrate binary functions
of two-input IMPLICATION, NOR, and XNOR logic gates.