Synthesis and spectroscopy of cyanotriacetylene (HC7N) in solid argon.

UV laser irradiations of cryogenic solid argon matrices doped with a mixture of acetylene and cyanodiacetylene (HC5N) resulted in the formation of a longer carbon-nitrogen chain, cyanotriacetylene (HC7N). The identification of this species was accomplished based on IR vibrational spectroscopy (including the study of isotopically labeled compounds), on electronic luminescence spectroscopy, and on theoretical predictions. Additionally, IR absorption bands recognized as due to HC7N were detected in photolysed Ar matrices doped with a cyanoacetylene/diacetylene mixture; this assignment was confirmed with the mass spectrometry of gases released upon the warm-up of the sample.

Photochemical synthesis of the cyanodiacetylene HC(5)N: a cryogenic matrix experiment.

The reactivity of intermolecular complexes cyanoacetylene:acetylene and dicyanoacetylene:acetylene, trapped in solid argon matrixes at 10 K and irradiated with vacuum UV, has been studied. FTIR measurements, together with (2)H, (15)N, (13)C labeling experiments and with density functional theory (DFT) calculations (B3LYP/aug-cc-pVTZ), pointed to the formation of cyanodiacetylene HC(5)N (cyanobutadiyne). This synthetic route is potentially important for chemical models of the Titan's atmosphere.

Cell adhesion to polymeric surfaces: experimental study and simple theoretical approach.

In a medium without serum, the initial adhesion of L1210 cells to nonsulfonated and sulfonated polymer surfaces was investigated. In the case of sulfonated polymer surfaces, the relative number of adhering cells strongly increases with an increase of the interfacial surface tension; that is, adhesion strongly depends on the surface density of sulfonic groups. However, in the case of nonsulfonated polymer surfaces, the relative number of adhering cells is high and independent of the interfacial surface tension. To extend the basic knowledge of these phenomena, a semi-empirical quantum chemical computational study was undertaken. Simple probe molecules were chosen that mimic the chemical properties of functional groups present on polymeric surfaces. The energies of interaction between these molecules and ones representing the midchain polypeptide building blocks were calculated. To discuss the steric effects involved in similar interactions on real surfaces, a simple model of polymeric surfaces was proposed. Also the interactions among such surfaces and the short hydrated polypeptide chain were studied at the molecular mechanics level of theory. The derived intermolecular energy parameter was found to change in parallel to the number of adhered cells within the two groups of substrata under study: nonsulfonated and sulfonated. The computational results suggest the possible existence of differently arranged cell membrane protein centers responsible for docking to these two types of surfaces.

Spectroscopic identification of 2,4-pyrimidinedithiol; an experimental matrix isolation and ab initio Hartree-Fock and density functional theory study.

2,4-Pyrimidinedithiol (the dithiol form of 2,4-dithiouracil) was generated by UV (lambda > 335 nm) irradiation of the dithione form of 2,4-dithiouracil isolated in low-temperature argon or nitrogen matrices. The IR and UV spectra of the photoproduct are reported. The dithiol form of 2,4-dithiouracil was identified by comparison of the experimental spectrum with the spectrum theoretically predicted for this form at the HF/6-31 (d,p) and DFT(B-3LYP)/6-31 (d,p) levels. This comparison resulted also in assignment of the bands observed in the IR spectrum of 2,4-pyrimidinedithiol to the theoretically predicted normal modes.