Abstract
Designing switchable materials with large contrasts of nonlinear optical properties has been the focus of research in recent decades because of their widespread applications. Redox-active metal complexes due to charge transfer excitation are suitable to produce switchable nonlinear optical (NLO) material. In this regard, we present here the redox switchable NLO response of active metal complexes of iron and cobalt. The geometric, electronic, molecular absorption, nonlinear optical properties, and switch “ON/OFF” style of these metal complexes are studied at the CAM-B3LYP/6-31 + G(d) level of theory. NLO responses of these redox metal complexes are described in terms of change in the charge transfer (CT) patterns by time dependent density functional theory (TD-DFT). The highest βo value of 301534 × 10−30 esu is noticed in [Fe-ethynyl-ZnP]1+ complex, because of obvious charge transfer transition from metal to ligand i.e meatal-ligand charge transfer (MLCT) in redox metal complex. In each redox metal isomeric pair, the greater hyperpolarizability value of individual isomer is quite consistent with its smaller energy gap (H-Lgap) between highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), low crucial excitation energy, and bathochromic shift of λmax. The remarkable βo contrasts of these isomeric redox complexes illustrate that they can be appropriate for effective redox-triggered NLO switches. Thus, the results reveal that these redox pair complexes show two-state switching “ON/OFF” effect.
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•Switchable NLO response of redox-active metal complexes of Fe and Co is studied.•Metal-ligand charge transfer (MLCT) and intra-ligand charge transfer (ILCT) in the complexes mark the contrast of NLO response.•These redox pair complexes show two-state switching “ON/OFF” effect.•The highest contrast in NLO response between redox pair is observed for [Fc-ethynyl-ZnP].•The highest βo value of 301534 × 10−30 esu is noticed in [Fc-ethynyl-ZnP]1+ complex.