A thorough understanding of the nonlinear optical properties of BODIPY/carborane/diketopyrrolopyrrole hybrid chromophores: module contribution, linear combination, one-/two-dimensional difference and carborane's arrangement

Abstract

In an attempt to enrich the understanding of essential structure–nonlinear optical (NLO) property correlations in multi-component photoactive boron dipyrromethene/closo-dodecaborane/diketopyrrolopyrrole (BOD/Cp/DPP) hybrid chromophores, three basic modules, three dyads, and five triads were systematically designed and comparatively investigated. Herein, the geometric and electronic structures, electronic absorption spectra, polarizabilities (α_ave) and first hyperpolarizabilities (β_tot) were calculated using density functional theory. It was found that the absorption spectrum and α_ave results of our current chromophores were highly modular, which can be efficiently deduced from the corresponding building blocks. The β_tot values were determined by the BOD module because of their dominant polarization mechanisms, rather than a general dependence on the molecular size/volume. Furthermore, we presented a comprehensive assessment of the evolution of the structure and photophysical (NLO) properties upon linear combination of basic functional modules, one-/two-dimensional geometric differences and carborane's differently substituted position deriving from the pristine rod-like BOD–Cp–DPP platform. The take home messages suggest that the quadratic NLO behaviors can be rationally tuned by the minor modifications in the structure. Overall, we believe that the proposed chromophores and even more the reasoning for their design/recognition will be helpful for the exploration of more efficient NLO materials than those currently available.