Photophysical behavior of systematically substituted (di-2-pyridylaminomethyl) benzene ligands and its Re(I) complexes: A combined experimental and theoretical approach

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2017-05, Vol.341, p.115-126
• Main Authors: Rohman, Mostofa Ataur, Sutradhar, Dipankar, Sangilipandi, S., Mohan Rao, K., Chandra, Asit K., Mitra, Sivaprasad
• Format: Article
• Language: English
• Subjects: (2-Pyridyl-aminomethyl) benzene Re(I) complex; Antenna system; Benzene; Charge transfer; Chemical bonds; Density functional theory; DFT calculation; Energy transfer and trapping; Fluorescence; Fluorescence spectroscopy; Hydrocarbons; Hydrogen bonding; Ligands; Mathematical analysis; Molecular orbitals; Optical properties; Physical properties; Time-resolved fluorescence
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2017.03.031

[Display omitted] •Investigated systems show interesting photophysics in DMSO–water mixture.•Inter-chromophoric interaction is present in highly substituted systems.•DFT calculation results support the experimental findings.•Strongly modulated photochemistry at low DMSO content (XDMSO=0.1–0.3).•Can lead in designing artificial photosynthetic antenna system by placing suitable trapping site. The photophysical behavior of a series of flexible di-2-pyridylaminomethyl substituted ligands systematically substituted on a rigid benzene core and their corresponding mono-metallic Re(I) complexes have been investigated by steady state and time-resolved fluorescence spectroscopy in different composition of DMSO–water binary solvent mixtures. Unusual fluorescence properties in lower DMSO content (XDMSO=0.1–0.3) solvent mixtures is consistent with fascinating property of DMSO, which is known to perturb the hydrogen bonding ability of water with the solute. Spin allowed inter-ligand π–π* transition is more apparent in (1, 3) substituted systems. The calculated spectroscopic parameters of the complexes are significantly different from the ligands, mainly due to ligand to metal charge transfer. The experimental observations are in very good agreement with the theoretical results obtained at B3LYP/6-31G(d,p)/LANL2DZ level of density functional theory (DFT) calculation. Natural bond orbital (NBO) analysis and examination of frontier molecular orbitals reveal that the basic architecture of the symmetrically substituted multi-chromophoric ligand can induce excitation energy hopping, similar to an artificial antenna system.