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Near‐IR Absorbing Ruthenium Complexes of Non‐Innocent 6,12‐Di(pyridin‐2‐yl)indolo[3,2‐ b ]carbazole: Variation as a Function of Co‐Ligands
Author(s) -
Panda Sanjib,
Ansari Md Asif,
Mandal Abhishek,
Lahiri Goutam Kumar
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201900719
Subject(s) - deprotonation , chemistry , ruthenium , crystallography , redox , bipyridine , electron paramagnetic resonance , density functional theory , photochemistry , stereochemistry , inorganic chemistry , crystal structure , computational chemistry , catalysis , organic chemistry , ion , physics , nuclear magnetic resonance
This article deals with the hitherto unexplored metal complexes of deprotonated 6,12‐di(pyridin‐2‐yl)‐5,11‐dihydroindolo[3,2‐ b ]carbazole (H 2 L). The synthesis and structural, optical, electrochemical characterization of dimeric [{Ru III (acac) 2 } 2 (μ‐L .− )]ClO 4 ([ 1 ]ClO 4 , S= 1/2), [{Ru II (bpy) 2 } 2 (μ‐L .− )](ClO 4 ) 3 ([ 2 ](ClO 4 ) 3 , S= 1/2), [{Ru II (pap) 2 } 2 (μ‐L 2− )](ClO 4 ) 2 ([ 4 ](ClO 4 ) 2 , S =0), and monomeric [(bpy) 2 Ru II (HL − )]ClO 4 ([ 3 ]ClO 4 , S =0), [(pap) 2 Ru II (HL − )]ClO 4 ([ 5 ]ClO 4 , S =0) (acac=σ‐donating acetylacetonate, bpy=moderately π‐accepting 2,2’‐bipyridine, pap=strongly π‐accepting 2‐phenylazopyridine) are reported. The radical and dianionic states of deprotonated L in isolated dimeric 1 + / 2 3+ and 4 2+ , respectively, could be attributed to the varying electronic features of the ancillary (acac, bpy, and pap) ligands, as was reflected in their redox potentials. Perturbation of the energy level of the deprotonated L or HL upon coordination with {Ru(acac) 2 }, {Ru(bpy) 2 }, or {Ru(pap) 2 } led to the smaller energy gap in the frontier molecular orbitals (FMO), resulting in bathochromically shifted NIR absorption bands (800–2000 nm) in the accessible redox states of the complexes, which varied to some extent as a function of the ancillary ligands. Spectroelectrochemical (UV/Vis/NIR, EPR) studies along with DFT/TD‐DFT calculations revealed (i) involvement of deprotonated L or HL in the oxidation processes owing to its redox non‐innocent potential and (ii) metal (Ru III /Ru II ) or bpy/pap dominated reduction processes in 1 + or 2 2+ / 3 + / 4 2+ / 5 + , respectively.