The effect of metal-to-ligand charge transfer on linear and nonlinear optical properties of hexaphyrin and metallo-hexaphyrins

Abstract

Charge transfer from metal to ligand has implications in various fields of chemistry, physics and biology. The manipulation of spin properties would be necessary for controlling charge transfer in spintronics and biological applications. Upon binding to the metal atoms (Ni, Cu, Au, etc.), the spin properties would be modulated in organic conjugated molecules of less intrinsic spin–orbit coupling (SOC) due to SOC coming from the heavy elements. Emission spectra calculation is necessary to validate them as suitable fluorescence quenchers. The nonlinear optical properties like first-order hyperpolarisability β and second-order hyperpolarisability γ calculations are important to find out their relation between fluorescence quenching and higher order nonlinear optical (NLO) properties. From the second-order NLO properties, we computed degenerate four-wave mixing (DFWM) component (${\gamma }^{(2)}(-\omega ;\omega ,\omega ,-\omega$)) and finally quadratic nonlinear refractive indices of the expanded porphyrins (EPs). How the linear and nonlinear optical properties are dependent on the SOC coming from the heavy materials (Ni, Cu, Au), and charge transfer process is the most interesting question to be addressed for their potential uses for various optoelectronic and spintronic applications.

GRAPHICAL ABSTRACT

Keywords:

• DFWM
• ISC
• SOC
• TDDFT
• NLO
• IFCT
• TDDFT

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

S.N. contributed to Conceptualisation, Methodology, Data Curation, Investigation, Formal analysis, Writing an original draft, Software, Visualisation, and Validation. M.D. contributed to Formal analysis, Writing of original drafts, Supervision, Resources, Project administration, and Funding acquisition.

Additional information

Funding

The authors acknowledge financial support from the Department of Science and Technology, Government of India, through a SERB Fast-Track Grant SB/FT/CS-164/2013 and IISER Kolkata for fellowship. We are also thankful to Dr. Kingsuk Mukhuti from HFML, Radboud University, The Netherlands, and Dr. Krishnayan Basuroy from Deutsches Elektronen-Synchrotron (DESY), Germany, for the fruitful scientific and technical discussion. Part of the analyses was done at the University of Hamburg.