Free Ethynylarsinidene and Ethynylstibinidene: Heavier Analogues of Nitrenes and Phosphinidenes.

Until now, there has been very little experimental evidence for the existence of free arsinidenes and stibinidenes, apart from the hydrides, AsH and SbH. Here, we report on photogeneration of triplet ethynylarsinidene, HCCAs, and triplet ethynylstibinidene, HCCSb, from ethynylarsine and ethynylstibine, respectively, in solid argon matrices. The products were identified using infrared spectroscopy and the associated UV absorption spectra are interpreted with the aid of theoretical predictions.

A DFT Study on the Excited Electronic States of Cyanopolyynes: Benchmarks and Applications.

Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HCN ( = 0-13) and dinitriles NCN ( = 0-14). The results of time-dependent density functional theory (TD-DFT) calculations are compared with the available gas-phase and noble gas matrix experimental data.

Unusual Quartet-Doublet Phosphorescence from the Phosphaethynyl Radical, CP.

We report the first detection of phosphorescence from the phosphaethynyl radical. This rare instance of quartet-doublet emission, studied here in solid argon, is presumably promoted by efficient intersystem crossing from the originally photoexcited doublet (B Σ ) to the adjacent second quartet state, 1 Δ. Vibronic progressions were traced for the a Σ -X Σ and a Σ -A П systems from their origins up to (v'=0)→(v''=5) and (v'=0)→(v''=2) bands, respectively.

An Efficient Photochemical Route Towards Triplet Ethynylphosphinidene, HCCP.

While the archetypal free phosphinidene, H-P, has been studied for over a century, reports on uncomplexed, univalent phosphorus compounds are very sparse. Here we demonstrate production of HCCP in solid argon through the UV-induced rearrangement and subsequent dehydrogenation of phosphapropyne, CH CP. Migration of H atoms along the CCP backbone of CH CP resulted in production of the previously unobserved species 1-phosphapropadiene, CH =C=PH, followed by ethynylphosphine, HCCPH .

Isomerization of cyanopropyne in solid argon.

Cyanopropyne, CH3-C[triple bond, length as m-dash]C-CN, is a simple molecule whose photochemistry is still unexplored. Here we investigate the UV photolysis of this astrophysically significant nitrile trapped in solid argon. The FTIR study was assisted with 15N-isotopic substitution data and with DFT-level computations including the analyses of ground- and excited-state potential energy surfaces.

Synthesis and Electronic Phosphorescence of Dicyanooctatetrayne (NCN) in Cryogenic Matrixes.

The rodlike 1,8-dicyano-octa-1,3,5,7-tetrayne (NCN) molecule was synthesized with UV-assisted coupling of rare-gas matrix-isolated cyanobutadiyne (HCN) molecules. Detection of NCN molecule was possible due to its strong orange-red (origin at 618 nm) electronic luminescence. Excitation spectra of this emission (ã Σ-X̃ Σ phosphorescence) gave access to studying the fully allowed H̃ Σ-X̃ Σ UV system of NCN.

Low Temperature Synthesis and Phosphorescence of Methylcyanotriacetylene.

This paper reports on UV-stimulated synthesis of methylcyanotriacetylene carried out in cryogenic rare gas matrixes via coupling of smaller precursors: propyne and cyanodiacetylene. The detection was possible due to the strong visible ã A' → X̃ A phosphorescence of CHCN, discovered in the course of this work. The ensuing measurements of electronic spectroscopy revealed the formally forbidden B̃ E-X̃ A system, as well as the allowed one Ẽ A-X̃ A, with origins at approximately 3.

Cryogenic Photochemical Synthesis and Electronic Spectroscopy of Cyanotetracetylene.

HCN is a molecule of astrochemical interest. In this study, it was produced in cryogenic Ar and Kr matrices from UV-photolyzed diacetylene/cyanodiacetylene mixtures. Its strong phosphorescence was discovered and served for the identification of the compound.

Electronic Spectroscopy of Methylcyanodiacetylene (CH C N).

The results of a study devoted to the electronic spectroscopy of gaseous, solid, and cryogenic matrix-isolated methylcyanodiacetylene (CH C N) are reported. UV absorption and optical phosphorescence spectra of the compound are described here for the first time, and the corresponding vibronic assignments are proposed. UV absorption, studied directly or through the excitation of phosphorescence, revealed the B˜   E--X˜   A system, very weak A˜   A -X˜   A bands, and a strong, broad absorption feature, tentatively identified as D˜   E-X˜   A .

Infrared and Raman Spectroscopy of Methylcyanodiacetylene (CH C N).

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH C N). Gas-phase, cryogenic matrix-isolated, and pure solid-phase substance was analyzed. Out of 16 normal vibrational modes, 14 were directly observed.

Density Functional Exploration of C4H3N Isomers.

Molecules having C4H3N stoichiometry are of astrophysical interest. Two of these, methylcyanoacetylene (CH3C3N) and its structural isomer allenyl cyanide (H2CCCHN), have been observed in interstellar space, while several more have been examined in laboratories. Here we describe, for a broad range of C4H3N isomers, density functional calculations (B3LYP/aug-cc-pVTZ) of molecular parameters including the energetics, geometries, rotational constants, electric dipole moments, polarizabilities, vibrational IR frequencies, IR absorption intensities, and Raman activities.

Cavity Ring Down Spectroscopy Measurements for High-Overtone Vibrational Bands of HC3N.

Overtone (5ν1 and 6ν1) and combination (4ν1 + ν3 and 4ν1 + ν2) vibrational bands of gaseous HC3N, located in the visible range (14,600-15,800 and 17,400-18,600 cm(-1)), were investigated by cavity ring-down absorption spectroscopy. The 5ν1 + ν3 and 5ν1 + ν2 combinations as well as the 6ν1 + ν5 - ν5 hot overtone band have also been identified, on the basis of previous overtone assignments. Absolute integrated intensity values and the ensuing oscillator strengths have been measured here for the first time; f values are typically confined between 4 × 10(-12) and 7 × 10(-11).

Quantum chemical study on HKrC₅N, HXeC₅N, and related rare gas compounds.

The recent identification of HRgC5N (Rg = Kr, Xe) in a cryogenic matrix calls for an in-depth theoretical study on these compounds. Here we present the results of CCSD(T), MP2, and DFT calculations concerning the molecular structure, stability, and vibrational spectroscopy. The procedure combining CCSD(T) calculations for variable H-Rg distances with the anharmonic description of the corresponding stretching vibration, based on a Morse-type potential energy function, was proposed and has led to good agreement between computational and experimental values for H-Rg stretching frequencies, at relatively low computational costs.

Formation and spectroscopy of dicyanotriacetylene (NC₈N) in solid Kr.

Thermally induced creation of dicyanotriacetylene (NC8N) was observed in solid krypton. Samples were obtained by cryogenic trapping of gaseous cyanoacetylene/Kr mixtures subjected to electric discharges. Strong a (3)Σ(+)(u) → X (1)Σ(+)(g) phosphorescence of NC8N is reported here for the first time; its vibronic structure permitted the measurement of several ground-state vibrational frequencies.

Ab initio studies of the structure and spectroscopy of CHNMg stoichiometry molecules and van der Waals complexes.

A high-level ab initio study was conducted over the range of tetraatomic molecules containing H, C, N, and Mg. Potential energy surfaces were analyzed, leading, for selected molecules, to the optimization of their geometry in the lowest singlet and triplet excited states. Reliable ground state rotational constants are given for the most stable species, namely, HMgNC and HMgCN, together with respective anharmonic vibrational frequencies of fundamental, overtone, and combination bands.

Structure, energetics, and infrared spectra of weakly bound HC(2n+1)N···HCl complexes. A theoretical study.

Three model systems, HCN···HCl, HC(3)N···HCl, and HC(5)N···HCl, have been investigated computationally with the use of the second-order Möller-Plesset (MP2) and the coupled cluster (with single and double excitations and noniterative inclusion of triples) methods. The global minima are linear hydrogen-bonded structures with HCl as a proton donor. Bent structures are proton-side complexes with HCl as an electron donor, while the bifurcated hydrogen bonds are predicted for t-shape complexes.

UV-induced growth of cyanopolyyne chains in cryogenic solids.

UV laser excitation of cryogenic solids doped with cyanoethyne, HC(3)N, led to an in situ creation of longer carbon-nitrogen chains, namely HC(5)N, C(4)N(2), and C(6)N(2), heralded by their strong visible luminescence. HC(5)N and C(4)N(2) molecules can form, most probably, within HC(3)N aggregates linked by hydrogen bonds, while the reaction occurring between two isolated, photochemically created C(3)N radicals yields C(6)N(2). This latter species, dicyanobutadiyne, is easily detected in Ar, Kr, N(2), as well as in parahydrogen solids.

Albumin adsorption on unmodified and sulfonated polystyrene surfaces, in relation to cell-substratum adhesion.

Albumin is commonly applied for blocking the adsorption of other proteins and to prevent the nonspecific adhesion of cells to diverse artificial substrata. Here we address the question of how effective these albumin properties are--by investigating unmodified and sulfonated polystyrene substrata with distinctly different wettabilities. As clearly shown with (125)I-radioisotopic assays, above a concentration of 10-20 μg/mL, the efficiency of bovine serum albumin (BSA) adsorption became markedly higher on the sulfonated surface than on the unmodified one.

Electronic absorption and phosphorescence of cyanodiacetylene.

Electronic absorption and emission spectra have been investigated for cyanodiacetylene, HC(5)N, an astrophysically relevant molecule. The analysis of gas-phase absorption was assisted with the parallel rare gas matrix isolation experiments and with density functional theory (DFT) predictions concerning the excited electronic states. Mid-UV systems B (1)Delta<--X (1)Sigma(+) (origin at 282.

IR low-temperature matrix, X-ray and ab initio study on L-isoserine conformations.

The IR low-temperature Ar and Kr matrix spectra of l-isoserine were registered for the first time and interpreted by means of the anharmonic DFT frequencies calculated at the B3LYP/aug-cc-pVTZ and B3LYP/aug-cc-pVDZ levels. 54 l-isoserine conformers were predicted to be stable at the B3LYP/aug-cc-pVDZ level. Population of the 8 most stable conformers was based on the QCISD/aug-cc-pVDZ energies, corrected for thermal anharmonic factors obtained at the B3LYP/aug-cc-pVDZ level.

Atomic force microscopy evidence for conformational changes of fibronectin adsorbed on unmodified and sulfonated polystyrene surfaces.

The effect of polystyrene surface polarity on the conformation of adsorbed fibronectin (FN) has been studied with atomic force microscopy. We demonstrated that bare sulfonated and nonsulfonated polystyrene surfaces featured similar topographies. After the FN adsorption, direct comparison of both types of substrata revealed drastically different topographies, roughness values, and also cell-adhesive properties.

IR low-temperature matrix and ab initio study on beta-alanine conformers.

For the first time the argon-matrix low-temperature FTIR spectra of beta-alanine are recorded. They reveal a quite complicated spectral pattern which suggests the presence of several beta-alanine conformers in the matrix. To interpret the spectra, the eighteen beta-alanine conformers, stable in the gas phase, are estimated at the B3LYP and MP2 levels combined with the aug-cc-pVDZ.

The C3N- anion: first detection of its electronic luminescence in rare gas solids.

The 193 nm laser irradiation of cyanoacetylene (HCCCN) that was isolated in rare gas solids led to a long-lived luminescence (origin at 3.58 eV), which was assigned to the a (3)Sigma(+)-X (1)Sigma(+) system of cyanoacetylide (CCCN(-)). The identification, which involved (15)N and (2)H isotopic substitution studies, is based on vibronic spacings in the phosphorescence spectrum (compared to previous infrared absorption measurements and to theoretical results regarding CCCN(-) vibrational frequencies), as well as on a BD(T)/cc-pVTZ prediction for the singlet-triplet energy gap in this anion (3.

Matrix isolation IR spectroscopic and ab initio studies of C(3)N(-) and related species.

Coupled cluster calculations were carried out for C(3)N(-), CCNC(-), C(3)N, CCNC, C(3)N(+), and C(3)O. They support the experimental identification of the C(3)N(-) ion by means of matrix isolation infrared (IR) spectroscopy. The anion was generated in electric discharges through the cyanoacetylene isotopomers HC(3) (14)N, HC(3) (15)N, and (2)HC(3)N, trapped in cryogenic rare gas matrices (Ne, Ar, Kr), and detected via its two most intense IR absorption bands, assigned to the nu(1) and nu(2) stretching vibrations.

C(5)N(-) anion and new carbenic isomers of cyanodiacetylene: a matrix isolation IR study.

Products of the vacuum-UV photolysis of cyanodiacetylene (HC(5)N) in solid argon -- the anion C(5)N(-), imine HNC(5), and the branched carbene C(4)(H)CN -- have been identified by IR absorption spectroscopy, in addition to the already discovered isonitrile HC(4)NC. Spectral assignments were assisted by deuterium substitution experiments, by BD(T) calculations, and by the results of a recent density functional theory study.