Describing excited states of [n]cycloparaphenylenes by hybrid and double-hybrid density functionals: from isolated to weakly interacting molecules

Abstract

We theoretically study the excited-state properties of cycloparaphenylenes ([n]CPPs) for a deeper understanding of their photochemical properties with increasing size n, being $$n = 6-12$$ the number of repeat units forming the nanoring. We apply hybrid (e.g., PBE0 and PBE0-1/3), double-hybrid (e.g., PBE0-DH and PBE-QIDH) and range-separated (e.g., $$\omega$$ B97X) functionals within a Time-Dependent (Tamm–Dancoff) Density Functional Theory framework. For the [6]CPP case, we concomitantly address changes in the set of selected excited states when going from an isolated molecule to a pair of self-assembled molecules, employing for that a dimer of parallel-like or tubular-like molecules according to the solid-state supramolecular organization found in real samples. These nanorings challenge standard theoretical methods due to the compromise needed between medium-range intramolecular (in isolated molecules) and long-range intermolecular (for weakly interacting pairs of molecules in condensed phases) interactions.