Efficient Synthesis of Fluorescent Coumarins and Phosphorous-Containing Coumarin-Type Heterocycles via Palladium Catalyzed Cross-Coupling Reactions

Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoumarins were performed, and the effect of the substituents in the aryl moiety was evaluated. The structures possessing promising fluorescent properties were successfully synthesized via Suzuki and Sonogashira cross-coupling. The synthetic protocol was also applied for the phosphorous chemoisomer of 3-phosphonocoumarin, 1,2-benzoxaphosphorin, and their carboxylate analogues. The optical properties of the arylated and alkynylated products were experimentally determined. The obtained quantum-chemical and experimental results give the possibility for a fine tuning of the optical properties of phosphorous-containing coumarin systems by altering the substituent at its C-6 position.

Study of the structural and optoelectronic properties of dye solar cells based on phosphonic acid anchoring by DFT functionals

The choice of the functional and an adequate basis set for reproducing the experimental data of T4-BTDA phosphonic acid-based dye is made by using six functionals and four atomic basis sets.

Individual control of singlet lifetime and triplet yield in halogen-substituted coumarin derivatives

The photophysical properties of three 3-diethylphosphonocoumarin derivatives are studied by transient absorption spectroscopy and DFT calculations. The measured lifetime of the first excited singlet state changes upon halogen substitution at the 6-position from 40 ps for the unsubstituted compound to 100 ps for Cl and 24 ps for Br. This observation is in clear contradiction with the estimated singlet–triplet quantum yield, which increases with atomic weight of the substituted atom and is usually referred as a heavy-atom effect. The DFT calculations give evidence that the main reason for this behavior is the different composition of the HOMO, while the LUMO is similar for all three compounds. The optical excitation leads to intramolecular charge transfer from the halogen lone pairs to the π* molecular orbital and thus to a significant change in the molecular dipole moment. Hence, the latter phenomenon in combination with the heavy-atom effect enables an independent control of singlet lifetime and singlet–triplet quantum yield in the studied 3-diethylphosphonocoumarin derivatives.

The photophysical properties of three 3-diethylphosphonocoumarin derivatives are studied by transient absorption spectroscopy and DFT calculations.

An experimental and theoretical study of solvent hydrogen-bond-donating capacity effects on ultrafast intramolecular charge transfer of LD 490

The excited-state intramolecular charge transfer (ICT) of LD 490 were investigated in different hydrogen-bond-donating solvents (α scale) on the basis of the Kamlet-Taft solvatochromic parameters (π*, α, β). The femtosecond transient absorption spectra and the kinetics decay rate reveal that with an increase of solvent's α capacity, the long-lived picosecond process, which is attributed to the ICT, becomes much faster. Combining with time-dependent density functional theory (TDDFT) calculations, we demonstrate that the enhancement of α acidity substantially increases the electronegativity of the carbonyl oxygen in LD 490, which strengthen excited-state intermolecular hydrogen bonding interactions and consequently facilitate the ICT process.