Change in energy of hydrogen bonds upon excitation of 6-aminocoumarin: TDDFT/EFP1 study

Abstract

Density functional theory (DFT)/time dependent density functional theory (TDDFT) calculations combined with the effective fragment potential (EFP) method have been carried out to study the electronic structure and the excited state properties of 6-aminocoumarin (6AC) with five water molecules (6AC-(H 2 O) 5 complex). Ground-state geometries are optimized using DFT with the B3LYP functional combined with cc-pVDZ basis sets and transition energies are computed with the same basis set and functional. One intermolecular hydrogen bond (HB) NÁ Á ÁH-O (type A) is formed between the amino group of 6AC and one water molecule, two intermolecular HBs CQOÁ Á ÁH-O (type B) are formed between the carbonyl group of 6AC and two water molecules, and two HBs of N-HÁ Á ÁO (type C), via participation of their amino hydrogen atoms, with the oxygen atoms of water molecules. The change in hydrogen bond energy, DE HB of the 6AC-(H 2 O) 5 molecule and DE HB for each HB of the 6AC-(H 2 O) 5 molecule are calculatedseparately. Upon excitation of the 6AC-(H 2 O) 5 complex, the A type HB is weakened with a decrease of 11.03 kJ mol À1 energy, whereas B and C type HBs are strengthened with increases of 5.28 and 18.14 kJ mol À1 energy, respectively. In this theoretical work, DE HB is calculated using the procedure proposed by T. Nagata et al. to calculate solute-solvent interaction energy in J. Chem. Phys., 2011, 134, 034110 and this study also confirmed again that intermolecular hydrogen bonds between the 6AC chromophore and aqueous solvents are strengthened, not cleaved upon electronic excitation, which is in accordance with Zhao's works Wiley Periodicals, Inc. J. Comput. Chem., 2011.

Solvation and Protonation of Coumarin 102 in Aqueous Media: A Fluorescence Spectroscopic and Theoretical Study

“…According to the Δ r G aq,complex 0 value for the S 0 state in Table , ∼ 80% of C102 is present in the form of the C O ···H 2 O water complex in the neutral aqueous solution of the dye. The significant weakening of the amino complex and the strengthening of the oxo complex are in accordance with previous findings, though in other theoretical studies on C102 and similar molecules, weak complexes were reported also in the S 1 state with very long hydrogen bonds.…”

Computational Analysis of Excited State Intramolecular Hydrogen Atom Transfer and Microsolvation Studies on 8-Acetyl-7-hydroxy-4-methylcoumarin using DFT and TDDFT

“…The phenomenon of hydrogen bonding has been illustrious for its eminence in various fields like photo-physics, photochemistry and biochemistry. The systematic study of hydrogen bonds is much essential for comprehending the photo-physical properties of some organic molecules which is having electron donor and acceptor demeanor at ground and excited states [1][2][3][4]. The effective fragment potential (EFP) method furnish a polarizable QM-based force field to characterize the intermolecular interactions.…”

Effect of Inter-molecular Hydrogen bond on ESIHT In 2, 2’-Dihydroxychalcone.

“…Out of two EFP methods EFP1 and EFP2, the original method EFP1, was initially evolved to explain aqueous solvation, by representing coulombic, induction and repulsive interactions [43][44]. Polarisable continuum model (PCM) is a solvation model for a Quantum Mechanical (QM) molecular system in which the solvent is symbolized as a continuum distribution of matter to describe the solvation effect on photo physical characteristics of biological and chemical chromophores at lower and higher energy states by implementing the DFT / TDDFT method [45][46].…”