Abstract
Optically active materials, including donor-acceptor systems, polymers, and porphyrin derivatives, are central to applications in photovoltaics, nonlinear optics, sensing, and bioimaging. Understanding their photophysical behavior is key to guiding molecular design and optimizing performance. In our laboratory, we combine Fourier-transform Raman spectroscopy (FT-Raman, 1064 nm), Resonance Raman (RR) spectroscopy, and Density Functional Theory (DFT) to investigate ground- and excited-state properties. This integrated approach enables us to probe vibrational modes, electronic transitions, and environment-dependent behavior. In donor-acceptor systems, FT-Raman and solvatochromic shifts reflect intrinsic ground-state polarity, supported by DFT-based geometry and charge-density analysis. In porphyrin derivatives, RR and TD-DFT uncover low-lying charge-transfer states that are not evident in UV–Vis spectra. In π-extended systems, enhanced light absorption is linked to a new π–π* excited state rather than additional charge transfer, as demonstrated by RR profiles and orbital analysis. These examples illustrate how spectroscopy theory collaboratively provides deep insight into the structural and electronic factors governing optical activity, enabling more informed development of photoactive materials.