The influence of the negative hyperconjugation is relevant for the analysis of the π-π* conjugation with the mono-substitution and di-substitution of H2C= by O= and/or HN= in trans-buta-1,3-diene?

Mechanistic Understanding and Reactivity Analyses for the Photochemistry of Disubstituted Tetrazoles

The photolysis of tetrazoles has undergone extensive research. However, there are still some problems to be solved in terms of mechanistic understanding and reactivity analyses, which leaves room for theoretical calculations. Herein, multiconfiguration perturbation theory at the CASPT2//CASSCF level was employed to account for electron correction effects involved in the photolysis of four disubstituted tetrazoles. Based on calculations of vertical excitation properties and evaluations of intersystem crossing (ISC) efficiencies in the Frank-Condon region, the combination of space and electronic effects is found in maximum-absorption excitation. Two types of ISC (¹ππ* → ³nπ*, ¹ππ* → ³ππ*) are determined in disubstituted tetrazoles, and the obtained rates follow the El-Sayed rule. Through mapping three representative types of minimum energy profiles for the photolysis of 1,5-, and 2,5-disubstituted tetrazoles, a conclusion can be drawn that the photolysis of tetrazoles exhibits reactivity characteristic of bond-breaking selectivity. Kinetic evaluations show that the photogeneration of singlet imidoylnitrene operates predominately over that in the triplet state, which can be confirmed by a double-well model in the triplet potential energy surface of 1,5-disubstituted tetrazole. Similar mechanistic explorations and reactivity analyses were also applied to the photolysis of 2,5-disubstituted tetrazole to unveil fragmentation patterns of nitrile imine generation. All computational efforts allow us to better understand the photoreactions of disubstituted tetrazoles and to provide useful strategies for regulating their unique reactivity.

Phosphorus-nitrogen compounds. Part 58. Syntheses, structural characterizations and biological activities of 4-fluorobenzyl-spiro(N/O)cyclotriphosphazene derivatives

The starting compound, tetrachloro-4-fluorobenzyl-spiro(N/O)cyclotriphosphazene (2), was synthesized from the substitution reaction of hexachlorocyclotriphosphazatriene (N₃P₃Cl₆; trimer; HCCP) with sodium 3-(4-fluorobenzylamino)-1-propanoxide (1). Reactions of spiro (2) with excess 1-(2-aminoethyl)-piperidine, 4-(2-aminoethyl)-morpholine, 1-(2-hydroxyethyl)piperidine and 4-(2-aminoethyl)morpholine yielded the fully substituted cyclotriphosphazene derivatives (2a-2d), respectively. Elemental analysis, mass spectrometry (ESI-MS), FTIR, ¹H-, ¹³C- and ³¹P-NMR data confirmed the structure of the new cyclotriphosphazenes (2a-2d); and the crystal structure of 2 was also identified by X-ray crystallography. The quantum mechanical DFT calculations of 2 were performed to estimate the geometry optimization, total energy, orientation of frontier molecular orbitals (HOMOs and LUMOs), and chemical parameters. In addition, antibacterial and antifungal activities of the fully substituted 4-fluorobenzyl-spiro(N/O)cyclotriphosphazenes (2a-2d) were investigated against G(+) and G(-) bacteria and fungi. Using agarose gel electrophoresis, the DNA cleavage activities of these phosphazenes on double-stranded plasmid DNA were evaluated. To evaluate the abilities of compounds 2a-2d to inhibit cell proliferation in different concentrations, the antiproliferative and antimigrative activities against prostate adenocarcinoma (PC3), breast cancer (MCF7) and colon cancer (HT29) cell lines were studied in vitro; and the compound 2c was determined to be the most efficient against the three cancer cells.Communicated by Ramaswamy H. Sarma.

Phosphorus-Nitrogen Compounds. Part 64. Comparative Reactions of Spiro and Ansa(N/O) Cyclotetraphosphazenes with Bulky (4-Fluorobenzyl) N/N and N/O Donor Type Bidentate Reagents: Structure, Stereogenic Properties and Cytotoxic activity Studies

The reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (1) (OCCP, tetramer) with an equimolar amount of sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L1) resulted in the formations of ferrocenyl-spiro-(2) and ferrocenyl-2-cis-4-dichloro-ansa-(3) cyclotetraphosphazenes. Both of the starting compounds...

Phosphorus-Nitrogen Compounds. Part 65. Novel diansa-spiro-cyclotetraphosphazenes: synthesis, characterization, bioactivity and electrochemical properties, fabrication of dye-sensitized solar cell studies

In this investigation, the substitution reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (tetramer, OCCP, 1) with sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L1) was found to yield the compounds, 2,4-ansa- (2) and spiro- (2) cyclotetraphosphazene derivatives. The...

Phosphorus–nitrogen compounds. Part 54. syntheses of chiral amino-4-fluorobenzyl-spiro(N/O)cyclotriphosphazenes: structural and stereogenic properties

Syntheses, spectral and crystallographic characterizations and stereogenic properties by ³¹P NMR spectra recorded with the addition of CSA, CD spectra and chiral HPLC of amino-4-fluorobenzylspiro(N/O)cyclotriphosphazenes were examined.

Phosphorus–nitrogen compounds. Part 42. The comparative syntheses of 2-cis-4-ansa(N/O) and spiro(N/O) cyclotetraphosphazene derivatives: spectroscopic and crystallographic characterization, antituberculosis and cytotoxic activity studies

Syntheses, structural properties and biological activities of ferrocenyl ansa- and spiro-cyclotetraphosphazenes were investigated.