Is this how bromine spiropyran salt is converted to merocyanine under UV irradiation? A look through the prism of quantum chemical calculations.

The stability of merocyanine forms formed under UV irradiation of a solution of a spiropyran salt, in which an organic part acts as a cation and a compact bromide ion as an anion, their photophysical properties, and the formation mechanism are studied in this work using time-dependent density functional theory. Theoretical calculations show that TTC and CTT are the most stable open forms (the difference in stability energies is 10.5 and 12.

Synthesis, Photochromic and Luminescent Properties of Ammonium Salts of Spiropyrans.

New salts of photochromic indoline spiropyrans capable of reversibly responding to UV radiation were synthesized to develop light-controlled materials. Photoinduced reactions of the synthesized compounds were studied using absorption and luminescence spectroscopies, and the quantum yields of photoisomerization and other spectral and kinetic characteristics were measured. It was shown that the light sensitivity and photostability of the synthesized compounds are considerably influenced by the length of the spacer between the indole and ammonium nitrogen atoms.

Synthesis of fullerenyl-1,2,3-triazoles by reaction of fullerenyl azide with terminal acetylenes.

Fullerenyltriazoles were synthesized by the interaction of azidofullerene with terminal acetylenes, in which the heterocyclic fragment is directly attached to the fullerene core. The electrochemical studies of the synthesized triazole-containing fullerenes have proved that the potentials of the first reduction peaks are shifted to a less cathodic region compared to unmodified C. According to theoretical calculations, synthesized fullerene C derivatives can be considered as promising acceptor components of organic solar cells.

Synthesis, photo and acidochromic properties of spiropyran-containing methanofullerenes.

Spiropyran-containing methanofullerenes able to rapidly and reversibly respond to optical and chemical stimuli were synthesized for the first time by the Bingel-Hirsch reaction and catalytic cycloaddition of diazo compounds to carbon clusters. The effects of substituent structure in the new hybrid molecule and the mode of spiropyran attachment to fullerene on the spectral kinetic properties and photo- and acidochromic behavior of the synthesized fullerene derivatives was established.

Twist-chair conformation of the tetraoxepane ring remains unchanged in tetraoxaspirododecane diamines.

A detailed structural analysis has been performed for N,N'-bis(4-chlorophenyl)-7,8,11,12-tetraoxaspiro[5.6]dodecane-9,10-diamine, CHClNO, (I), N,N'-bis(2-fluorophenyl)-7,8,11,12-tetraoxaspiro[5.6]dodecane-9,10-diamine, CHFNO, (II), and N,N'-bis(4-fluorophenyl)-7,8,11,12-tetraoxaspiro[5.

How the oxazole fragment influences the conformation of the tetraoxazocane ring in a cyclohexanespiro-3'-(1,2,4,5,7-tetraoxazocane): single-crystal X-ray and theoretical study.

Single crystals of (2S,5R)-2-isopropyl-5-methyl-7-(5-methylisoxazol-3-yl)cyclohexanespiro-3'-(1,2,4,5,7-tetraoxazocane), CHNO, have been studied via X-ray diffraction. The tetraoxazocane ring adopts a boat-chair conformation in the crystalline state, which is due to intramolecular interactions. Conformational analysis of the tetraoxazocane fragment performed at the B3LYP/6-31G(d,2p) level of theory showed that there are three minima on the potential energy surface, one of which corresponds to the conformation realized in the solid state, but not to a global minimum.

Aminomethylation of Fullerene C with N,N',N″-Triaryl- or N,N',N″-Trihetaryl-1,3,5-perhydrotriazines in the Presence of EtMgBr and Ti(Oi-Pr).

A new method for the functionalization of fullerenes based on the reaction between in situ generated aryl- or hetaryl-containing 1,3,5-perhydrotriazines and EtMgBr in the presence of Ti(Oi-Pr) has been developed. The cleavage of the triazine ring under previously developed conditions1-6 results in the formation of aminomethylated derivatives of fullerene C with high yields (80-90%) and selectivity (∼90%).

Diastereotopic splitting in the 13C NMR spectra of sulfur homofullerenes and methanofullerenes with chiral fragments.

Using gauge-invariant atomic orbital PBE/3ζ quantum chemistry approach, (13)C NMR chemical shifts and diastereotopic splittings of sp(2) fullerenyl carbons of a number of sulfur homofullerenes and methanofullerenes have been predicted and discussed. An anisochrony of fullerene carbons is caused by a chiral center of attached moieties. Clearly distinguishable diastereotopic pairs (from 8 to 11) of fullerenyl carbons of homofullerenes were observed.

Homo- and methano[60]fullerenes with chiral attached moieties--1H and 13C NMR chemical shift assignments and diastereotopicity effects.

(1)H and (13)C NMR chemical shift predictions of homo- and methano[60]fullerenes containing chiral centers in attached fragment were made using the two-dimensional NMR technique (HH COSY, (1)H-(13)C HSQC and HMBC) and the quantum chemistry GIAO calculation method in the PBE/3ζ approach. The influence of a chiral substituent on the (13)C chemical shifts of diastereotopic fullerene carbons was estimated by comparing the calculated and experimental (13)C NMR spectra. The resonances of the fullerene carbons in α-, β- and δ-positions relative to the position of the substituent exhibit the greatest diastereotopic splitting.

How reliable are GIAO calculations of 1H and 13C NMR chemical shifts? A statistical analysis and empirical corrections at DFT (PBE/3z) level.

Reliability of calculated (1)H and (13)C NMR chemical shifts for various classes of organic compounds obtained with gauge-invariant atomic orbital (GIAO) approach has been studied at the PBE/3ζ level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts δ(H,calc) = δ(PBE/3ζ) - 0.08 ppm (RMS 0.

1H and 13C NMR chemical shift assignments of spiro-cycloalkylidenehomo- and methanofullerenes by the DFT-GIAO method.

The (1)H and (13)C NMR chemical shifts of spiro-cycloalkylidene[60]fullerenes were assigned using experimental NMR data and the Density Functional Theory (DFT)-Gauge Independence Of Atomic Orbitals method (GAIO) calculation method in the Perdew Burke Ernzerhof (PBE)/3z approach. The calculated values of the (13)C NMR chemical shifts adequately reproduce the experimental values at this quantum chemistry approach. Similar assignments will be helpful for (13)C NMR spectral analysis of homo- and methano[60]fullerene derivatives for structure elucidation and to determine the influence of fullerene frames on substituents and the influence of substituents on fullerene cores.