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

Author(s)

Sanches de Araujo, Adalberto V. ; Rangel, Clara J. ; Ando, Romulo A.

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 127, n. 51, p. 8-pg., 2023-12-18.

Abstract

The resonant Raman (RR) and resonant SERS spectra of the thiadiazole-based dye dibromobenzo[c]-1,2,5-thiadiazole (DBTD) were studied through multiconfigurational XMS-CASPT2/CASSCF and experimental methods in solution. The results indicate that the S-1 excited state of DBTD is described by pi -> pi* with internal CT from the benzene ring to the thiadizole. In resonance conditions at 364 nm, the RR spectrum shows intensifications in modes that describe extensive geometrical changes at both the benzene ring and the thiadiazole region, indicating an internal CT character to the S-1. The SERS spectra observed on gold and silver nanoparticles indicate different adsorption geometries, which leads to distinct enhancement patterns on the spectra with varying excitation energy. It evidences the major contribution of the chemical enhancement mechanism on the spectra from a metal -> DBTD CT state, as confirmed by the simulated spectra. This theoretical approach proved strong in the prediction of the main features of the observed experimental resonant Raman and SERS spectra indicating a potential for adequate description of the chemical mechanism of SERS. (AU)

• FAPESP's process: 21/07031-5 - Multiconfigurational Calculations in the Description of Excited States Dynamics and its Correlation with Resonance Raman Spectroscopy
• Grantee: Adalberto Vasconcelos Sanches de Araújo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/21070-5 - Vibrational spectroscopy with spatial resolution
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants