AM1 calculations on equilibrium and transition state geometries of keto and enol forms of glitazones were carried out and compared with those of some carbonyl compounds. The results show that the energy requirements for enolisation of glitazones are much higher than the standard carbonyl systems. Neither the ring system, nor the additional functional groups in thiazolidinedione terminal ring fa...

The title Schiff base compound, 0.57C(17)H(12)FNO·0.43C(17)H(12)FNO, reveals both the enol (OH) and keto (NH) tautomeric forms with occupancies of 0.57 (6) and 0.43 (6), respectively. The tautomeric forms are stabilized by intra-molecular O-H⋯N (enol) and N-H⋯O (keto) hydrogen bonds. The dihedral angle between the naphthalene ring system and the benzene ring is 32.76 (1)°.

A comprehensive picture of the ultrafast nonradiative decay mechanisms of three cytosine tautomers (amino-keto, imino-keto, and amino-enol forms) is revealed by high-level ab initio potential energy calculations using the multistate (MS) CASPT2 method and also by on-the-fly excited-state molecular dynamics simulations employing the CASSCF method. To obtain a reliable potential energy profile al...

The enol tautomers of the aromatic oc-keto acids combine instantaneously and reversibly with borate to form complexes of a mixed ester-anhydride structure, thereby displacing the apparent keto-enol equilibrium in favor of the enol tautomer. The enol tautomer and its borate complex have strong absorption in the 300 ml* region (1). This strong absorption is the basis of the spectrophotometric met...

Metal-free organic triplet emitters are an emerging class of semiconducting material. Among them, molecules with tunable emission responsive to environmental stimuli have shown great potential in solid-state lighting, sensors, and anti-counterfeiting systems. Here, a novel excited-state intramolecular proton transfer (ESIPT) system is proposed showing the activation thermally activated delayed ...

Thiotropolone isolated in argon and xenon matrices (as monomers) or a neat solid the crystalline amorphous state) at low temperature was found to exist only thione-enol form. Visible light irradiation (λ ≥ 400 nm) leads → thiol-keto tautomerization under conditions 15 K. The assignment of IR spectra two thiotropolone tautomers (thione-enol thiol-keto) carried out with support B3LYP/6-311+G(2d,p...

In this study we report about two novel azomethine–BODIPY dyads 1 and 2. The two dyads have been, respectively, synthesized by covalent tethering of tautomeric ortho-hydroxy aromatic azomethine moieties including N-salicylideneaniline (SA) and N-naphthlideneaniline (NA) to a BODIPY fluorophore. Both of the two dyads 1 and 2 show enol-imine (OH) structures dominating in the crystalline state. Dy...

abstract:turmeric is a member of the ginger family (zingiberaceae), which is extensively used as a spice, food preservative and colouring material. curcumin is a main bioactive natural compound derived from the rhizome of this plant. curcumin can exist in several tautomeric forms, keto and enol. the keto form is more stable than enol form. silyl ethers have proven to be versatile substrates for...

The excited-state dynamics of photoexcited diethylamino hydroxybenzoyl hexyl benzoate (DHHB), a UVA absorber widely used in sunscreen formulations, are studied with transient electronic and vibrational absorption spectroscopy methods four different solvents. In the polar solvents methanol, dimethyl sulfoxide (DMSO), acetonitrile, strong stimulated emission (SE) is observed at early time delays ...