Vibrationally Resolved Absorption, Fluorescence, and Preresonance Raman Spectroscopy of Isolated Pyronin Y Cation at 5 K.

Exploring how charge-changing affects the photoluminescence of small organic dyes presents challenges. Here, helium tagging photodissociation (PD) action spectroscopy in the gas phase and dispersed laser-induced fluorescence (DF) spectroscopy in the solid Ne matrix are used to compare the intrinsic photophysical properties of pyronin Y cation [PY] and its one electron-reduced neutral radical [PY] at 5 K. Whereas the cation shows efficient visible photoluminescence, no emission from the neutral, in line with theoretical predictions, was detected.

Hydrogen-Atom-Assisted Uphill Isomerization of -Methylformamide in Darkness.

-Methylformamide, HC(O)NH(CH), is the smallest amide detected in the interstellar medium that can exist as and isomers. We performed reactions of H atoms with -NMF in solid -hydrogen at 3.3 K and found that the -NMF isomer, which has higher energy, increased continuously in darkness, demonstrating a previously overlooked and seemingly unlikely isomerization of prebiotic molecules through H-atom tunneling reactions in the absence of light.

Triggering near-infrared luminescence of vanadyl phthalocyanine by charging.

Probing electrofluorochromism (EFC) at the molecular level remains challenging. Here we study the strongly charge state-dependent photoluminescence of vanadyl phthalocyanine. We report vibrationally resolved absorption and laser-induced fluorescence (LIF) spectra of samples comprising both the mass-selected neutral molecule (VOPc⋅, a stable radical) and its cation produced upon electron ionization (EI) isolated in 5 K neon matrices.

Vibrationally Resolved Absorption and Luminescence Spectra of Mass-Selected Free-Base and Zinc Phthalocyanine Radical Cations Isolated in Solid Ne.

We report the first vibrationally well-resolved absorption and laser-induced fluorescence spectra of the radical cations of free-base phthalocyanine (HPc) and zinc phthalocyanine (ZnPc) isolated in 5 K neon matrices and compare them to the spectral properties of the corresponding neutrals. The samples were generated by low-energy deposition of the mass-selected ions. The spectra are also discussed in terms of time-dependent density functional theory calculations and compared with recently reported scanning tunneling microscopy-induced single-molecule luminescence of the same species adsorbed on NaCl-covered Au(111) or Ag(111) single crystal supports.

Photoactivated Refractive Index Anisotropy in Fluorescent Thiophene Derivatives.

The optical control of anisotropy in materials is highly advantageous for many technological applications, including the real-time modulation of another light signal in photonic switches and sensors. Here, we introduce three thiophene derivatives with a donor-acceptor structure, which feature different positions of an electron-acceptor nitrile group, and both photoalignment and luminescence properties. Quantum chemical calculations highlight the presence of -forms stable at room temperature and metastable -isomers.

Infrared Spectra of ()- and ()-CHC(CH)I Radicals Produced upon Photodissociation of ()- and ()-(CHI)HC═C(CH)I in Solid Hydrogen.

Ozonolysis of isoprene to produce Criegee intermediates such as methyl vinyl ketone oxide (MVKO), CHC(CH)OO, is an important process in atmospheric chemistry. MVKO was recently produced and identified in laboratories after photolysis of a gaseous mixture of 1,3-diiodo-but-2-ene, (CHI)HC═C(CH)I, and O, but the mechanism of its formation remains unexplored. We synthesized pure ()- and ()-1,3-diiodo-but-2-ene and measured their distinct IR spectra.

Hydrogen abstraction in astrochemistry: formation of ˙CHCONH in the reaction of H atom with acetamide (CHCONH) and photolysis of ˙CHCONH to form ketene (CHCO) in solid para-hydrogen.

Acetamide (CH3CONH2) is the largest molecule containing an amide bond that has been detected in an interstellar medium; it is considered to be a precursor for complex organic molecules (COM). We utilized the advantages of a para-hydrogen (p-H2) quantum-solid matrix host to perform efficient reactions of hydrogen atoms with CH3CONH2. The H-abstraction reaction from the methyl group of CH3CONH2 to produce the 2-amino-2-oxoethyl radical, ˙CH2CONH2, was observed as the sole reaction channel in solid p-H2 at 3.

Hydrogen-atom tunneling reactions with methyl formate in solid para-hydrogen: Infrared spectra of the methoxy carbonyl [•C(O)OCH] and formyloxy methyl [HC(O)OCH•] radicals.

We investigated the reaction of methyl formate, HC(O)OCH, with hydrogen atoms in solid para-hydrogen (p-H) at 1.74 and 3.3 K with infrared absorption spectroscopy.

Hydrogen Abstraction/Addition Tunneling Reactions Elucidate the Interstellar HNCHO/HNCO Ratio and H Formation.

Formamide (HNCHO) is the smallest molecule possessing the biologically important amide bond. Recent interstellar observations have shown a strong correlation between the abundance of formamide and isocyanic acid (HNCO), indicating that they are likely to be chemically related, but no experiment or theory explains this correlation satisfactorily. We performed H + HNCHO reactions in a -hydrogen quantum-solid matrix host and identified production of HNCO and HNCO from hydrogen-abstraction reactions.

Low-Molecular Push-Pull Pyrazoline Derivatives: Solvatochromic Effect and Theoretical Insights into Dye-based Molecular Engineering.

Intermolecular interactions between dyes and solvents are essential in understanding a number of phenomena. In this contribution, we focused on similarities and differences between two molecules belonging to the same pyrazoline derivatives group: the small and rigid- 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1 H-pyrazole (DCNP) molecule and the quite long and flexible one of (4-(2-(1-phenyl-4,5-dihydro-1 H-pyrazol-3-yl)vinyl)benzylidene) malononitrile (PY-PhdiCN). We experimentally show and use theoretical calculations to prove that extension of π-connector significantly changes the electrostatic potential distribution, which results in delocalization of negative charge along the whole donor group and increases potential surface of interaction with solvent molecules giving large spectral shifts.

Photodissociation of CFICFI in solid para-hydrogen: infrared spectra of anti- and gauche-˙CFI radicals.

The photolysis of 1,2-diiodotetrafluoroethane (CF2ICF2I) has served as a prototypical system in ultrafast reaction dynamics. Even though the intermediates, anti- and gauche-iodotetrafluoroethyl (˙C2F4I) radicals, have been characterized with electron diffraction and X-ray diffraction, their infrared spectra are unreported. We report the formation and infrared identification of these radical intermediates upon ultraviolet photodissociation of CF2ICF2I in solid para-hydrogen (p-H2) at 3.

All-Optical Switching and Two-States Light-Controlled Coherent-Incoherent Random Lasing in a Thiophene-Based Donor-Acceptor System.

We describe herein the synthesis and characterization of a thiophene-based donor-acceptor system, namely (E)-2-(4-nitrostyryl)-5-phenylthiophene (Th-pNO ), which was prepared under Horner-Wadsworth-Emmons conditions. The UV/Vis absorption bands, including the intramolecular charge transfer (ICT) band, were fully assigned using DFT and TD-DFT computations. The results of both efficient third-order nonlinear optical properties and light-amplification phenomena are presented.

Infrared absorption spectra of partially deuterated methoxy radicals CHDO and CHDO isolated in solid para-hydrogen.

The investigation of partially deuterated methoxy radicals is important because the symmetry lowering from C to C provides new insights into the couplings between rovibronic states via Jahn-Teller and spin-orbit interactions. The vibrational spectrum of the partially deuterated methoxy radical CHDO in a matrix of p-H has been recorded. This species was prepared by irradiating a p-H matrix containing deuterated d-nitritomethane (CHDONO) at 3.

Structural and spectroscopic characterization of DMF complexes with nitrogen, carbon monoxide, ammonia and water. Infrared matrix isolation and theoretical studies [corrected].

An infrared spectroscopic and MP2/6-311++G(2d,2p) study of the complexes between N,N-dimethylformamide (DMF) and nitrogen, carbon monoxide, water, ammonia trapped in solid argon matrices is reported [corrected]. The 1:1 molecular complexes have been identified in the DMF/B/Ar matrices (B=N, CO, HO, NH); their structures were determined by comparison of the spectra with the results of calculations. The analysis of the experimental and theoretical data indicate that the DMF-N, CO complexes present in the matrices are stabilized by (C=)O⋯N and (C=)O⋯C van der Waals interactions.

Reaction of H + HONO in solid para-hydrogen: infrared spectrum of ˙ONH(OH).

Hydrogenation reactions in the N/O chemical network are important for an understanding of the mechanism of formation of organic molecules in dark interstellar clouds, but many reactions remain unknown. We present the results of the reaction H + HONO in solid para-hydrogen (p-H) at 3.3 K investigated with infrared spectra.

Vibrational, XRD and (13)C NMR studies of DL-phenylglycinium methanesulfonate crystal.

A new crystal formed by DL-phenylglycine and methanesulfonic acid (PGLYMS) was obtained and studied by X-ray diffraction, IR and Raman spectroscopy, solid state NMR and DSC methods. Additionally, theoretical computations for the phenylglycine cation were carried out (DFT/B3LYP/aug-cc-pVDZ). Our results show that PGLYMS does not exhibit any phase transitions and crystallizes in the P21/c space group of monoclinic system (Z=4).

Donor-Acceptor Complexes between Ammonia and Sulfur Trioxide: An FTIR and Computational Study.

The complexes of ammonia with sulfur trioxide have been studied using FTIR matrix isolation spectroscopy and DFT/B3LYP calculations with the aug-cc-pVTZ basis set. The NH3/SO3/Ar matrixes were prepared in two different ways. In one set of experiments the matrix was prepared by the simultaneous deposition of the NH3/Ar mixture and SO3 vapor from the thermal decomposition of K2S2O7.

Isomers of the acetic acid-water complex trapped in an argon matrix.

The complexes of acetic acid (AcOH) with water have been studied using FTIR matrix isolation spectroscopy and DFT/B3LYP, DFT/B3LYP-D, and MP2 calculations with the aug-cc-pVTZ basis set. The AcOH/H2O/Ar matrices were prepared in two different ways. In one set of experiments, the vapor above a solid AcOH sample, cooled to 203 K, was diluted with H2O/Ar mixture in the vacuum chamber of the cryostat, and the mixture was solidified on the target.

Clustering of simple aminosulfonic acids--electrospray ionization mass spectrometric study.

Rationale: Aminosulfonic acids are structurally related to amino acids as bifunctional compounds. Some of them like taurine and homotaurine play important roles in biology. Although there is a vast literature devoted to the electrospray ionization mass spectrometric (ESI-MS) study of amino acid aggregation, no such study has been performed so far for aminosulfonic acids.