Simulation of charge-transfer, UV-VIS and resonance Raman spectra of push–pull systems: a TDDFT and CASPT2 comparison

Abstract

Time-Dependent Density-Functional Theory (TDDFT) and Extended Multi-State Complete Active Space Second-Order Perturbation Theory (XMS-CASPT2) methods, together with augmented correlation-consistent polarizable valence double-ζ (aug-cc-pVDZ) basis sets, were applied to simulate the...

Multiconfigurational Calculations and Experimental Resonant Raman/SERRS of a Donor–Acceptor Thiadiazole Dye

“…While density functional theory (DFT) methods provide excellent results for ground-state properties at lower computational cost, the study of systems in which excited-state properties are relevant reveals the need for theoretical methods that take into account the multiconfigurational nature of the electronic states of the molecules, , especially in molecular complexes containing transition metals . The use of multiconfigurational (MC) methods over the more common methods based on time-dependent (TD)-DFT benefits the description of the electronic structure and geometry of the excited states, , yielding more reliable results on the simulated spectra .…”

“…While density functional theory (DFT) methods provide excellent results for ground-state properties at lower computational cost, the study of systems in which excited-state properties are relevant reveals the need for theoretical methods that take into account the multiconfigurational nature of the electronic states of the molecules, , especially in molecular complexes containing transition metals . The use of multiconfigurational (MC) methods over the more common methods based on time-dependent (TD)-DFT benefits the description of the electronic structure and geometry of the excited states, , yielding more reliable results on the simulated spectra . The calculation of the RR and of the CM enhancement effects on SERS employing high-level MC methods such as CASPT2/CASSCF permits a deep interpretation of such systems that guides the recognition of the observed physical chemistry that comes from the interaction of the analyte and the light or the adsorbate and the metallic surface .…”

“…13 The use of multiconfigurational (MC) methods over the more common methods based on time-dependent (TD)-DFT benefits the description of the electronic structure and geometry of the excited states, 14,15 yielding more reliable results on the simulated spectra. 12 The calculation of the RR and of the CM enhancement effects on SERS employing high-level MC methods such as CASPT2/CASSCF permits a deep interpretation of such systems that guides the recognition of the observed physical chemistry that comes from the interaction of the analyte and the light or the adsorbate and the metallic surface. 16 Employing these methods should culminate in a reliable computational approach to describe the shape of the RR and SERS spectra.…”

“…At the optimized geometries, the vertical absorption spectrum of DBTD was calculated at the extended multistate complete active space perturbation theory at the 2ndorder (XMS-CASPT2) level of theory, 33 with a zero-order state-averaged (SA) CASSCF wave function, 34 with an active space containing nine π and π* valence orbitals and ten electrons (CAS(10,9)). The same was done with the model DBTD-M 2 with an expanded active space adding the HOMOlike orbital of the M 2 metal dimer and the σ bond orbitals of the complex, accounting for a CAS (12,11) active space.…”

Absorption Spectra of p-Nitroaniline Derivatives: Charge Transfer Effects and the Role of Substituents

“…It is structurally simple, has strong solvatochromism [28][29][30][31][32], characteristic optical properties [33][34][35][36][37], and has several applications [38]. For these reasons, pNA has − − been widely investigated [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], although it is still an active area of study, e.g., two newly pNA-based polymers recently synthesized attracted attention due to their potential applications. One is the poly(aniline-co-p-nitroaniline) or PANA, an anticorrosive pigment [57,58].…”