Characterization of Triplet State of Cyanine Dyes with Two Chromophores Effect of Molecule Structure

Quantum yields (fT) and energies (ET) of the first triplet state T1 for four molecules of cyanine dyes with two chromophores (BCDs), promising photoactive compounds for various applications, for example, as photosensitizers in photodynamic therapy (PDT) and fluorescence diagnostics (FD), were studied in 1-propanol solutions by steady-state and time-resolved optical absorption techniques. BCDs differ by the structure of the central heterocycle, connecting the chromophores. The heterocycle structure is responsible for electron tunneling between chromophores, for which efficiency can be characterized by splitting of the BCD triplet energy levels. It was shown that the increase in the tunneling efficiency reduces ET values and increases fT values. This aspect is very promising for the synthesis of new effective photosensitizers based on cyanine dyes with two interacting chromophores for various applications, including photodynamic therapy.

Automated summary

The quantum yields (fT) and energies (ET) of the first triplet state (T1) were investigated for four cyanine dye molecules with two chromophores (BCDs) in 1-propanol solutions. These BCDs have potential applications as photosensitizers in photodynamic therapy (PDT) and fluorescence diagnostics (FD). The heterocycle structure connecting the chromophores plays a crucial role in electron tunneling efficiency, which can be characterized by the splitting of the BCD triplet energy levels. Increasing the tunneling efficiency was found to decrease ET values and increase fT values, indicating the potential synthesis of new effective photosensitizers based on cyanine dyes for various applications, including photodynamic therapy.