Visible Absorptions of Potential Diffuse ISM Hydrocarbons: C9H9 and C9H5 Radicals

The laboratory detection of previously unobserved resonance-stabilized C9H5 and C9H9 radicals in the supersonic expansion of a hydrocarbon discharge source is reported. The radicals are tentatively assigned as acetylenic-substituted cyclopentadienyl C9H5 and vinyl-substituted benzyl C9H9 species. They are found to feature visible absorption bands that coincide with a few very weak diffuse interstellar bands toward HD183143 and HD204827

Gas Phase Detection of Benzocyclopropenyl

The gas phase detection of benzocyclopropenyl is reported. In this aromatic resonance stabilized radical, a large angular strain is present due to a three-membered ring annelated to a benzene. The resonant two-color two-photon ionization technique is used to record the D1(2A2) ← D0(2B1) electronic transition of this radical after the in situ synthesis in a discharge source. The spectrum features absorptions up to 3300 cm–1 above the origin band at 19 305 cm–1. Benzocyclopropenyl is possibly the major product of the bimolecular reaction of benzene and an atomic carbon at low temperatures

Electronic spectra of linear HC5_5H and cumulene carbene H2_2C5_5

The $1 ^3\Sigma_u^- \leftarrow X^3\Sigma_g^-$ transition of linear HC$_5$H (A) has been observed in a neon matrix and gas phase. The assignment is based on mass-selective experiments, extrapolation of previous results of the longer HC$_{2n+1}$H homologues, and density functional and multi-state CASPT2 theoretical methods. Another band system starting at 303 nm in neon is assigned as the $1 ^1 A_1 \leftarrow X ^1 A_1$ transition of the cumulene carbene pentatetraenylidene H$_2$C$_5$ (B).Comment: 7 pages, 4 figures, 5 table

Salivary Metabolomics for Oral Precancerous Lesions: A Comprehensive Narrative Review

Oral submucous fibrosis (OSMF) is a chronic, potentially malignant disorder of the oral cavity, primarily associated with the consumption of areca nut products and other risk factors. Early and accurate diagnosis of OSMF is crucial to prevent its progression to oral cancer. In recent years, the field of metabolomics has gained momentum as a promising approach for disease detection and monitoring. Salivary metabolomics, a non-invasive and easily accessible diagnostic tool, has shown potential in identifying biomarkers associated with various oral diseases, including OSMF. This review synthesizes current literature on the application of salivary metabolomics in the context of OSMF detection. The review encompasses a comprehensive analysis of studies conducted over the past decade, highlighting advancements in analytical techniques, metabolomic profiling, and identified biomarkers linked to OSMF progression. The primary objective of this review is to provide a critical assessment of the feasibility and reliability of salivary metabolomics as a diagnostic tool for OSMF, along with its potential to differentiate OSMF from other oral disorders. In conclusion, salivary metabolomics holds great promise in revolutionizing OSMF detection through the identification of reliable biomarkers and the development of robust diagnostic models. However, challenges such as sample variability, validation of biomarkers, and standardization need to be addressed before its widespread clinical implementation. This review contributes to a comprehensive understanding of the current status, challenges, and future directions of salivary metabolomics in the realm of OSMF detection, emphasizing its potential impact on early intervention and improved patient outcomes

Electronic Spectroscopy of Resonantly Stabilized Aromatic Radicals : 1-Indanyl and Methyl Substituted Analogues

The gas-phase electronic spectra of two resonantly stabilized radicals, 1-indanyl (C9H9) and 1-methyl-1-indanyl (C10H11), have been recorded in the visible region using a resonant two-color two-photon ionization (R2C2PI) scheme. The D1(A″) ← D0(A″) origin bands of 1-indanyl and 1-methyl-1-indanyl radicals are observed at 21157 and 20565 cm–1, respectively. The excitation of a′ vibrations in the D1 state is observed up to ∼1500 cm–1 above the origin band in both cases. The experimental assignments are in agreement with DFT and TD-DFT calculations. The R2C2PI spectrum recorded at m/z = 131 amu (C10H11) features three additional electronic transitions at 21433, 21369, and 17989 cm–1, which are assigned to the origin bands of 7-methyl-1-indanyl, 2,3,4-trihydronaphthyl, and methyl-4-ethenylbenzyl radicals, respectively

Investigation on the Origin of Dispersion Interaction in Weakly Bound Phenylacetylene•CnHm clusters using dispersion corrected density functional calculations

Dispersion interaction is the attractive forces between an instantaneous dipole and induced dipole, generated due to the correlated movement of electrons in interacting molecules. Dispersion dominated intermolecular interaction has been the topic of interest among scientific communities to describe physical, chemical, and biological phenomena of diverse chemical systems such as crystal packing, protein folding, conformations and configurations of many biomolecules and polymers. Understanding the nature and origin of the interaction requires both experimental and theoretical investigations and a mutual agreement between them. In this project, we are going to investigate the dispersion interaction of PHA-CnHm clusters, where PHA is a non-polar S molecule with π-electron density which can form C-H/π bound complexes which are significantly different than the conventional hydrogen bonds like O-H/π or N-H/π. We have used density functional theory with dispersion correction using B3LYP-D3, PBE0-D3 functionals with def2-TZVPP and aug-cc-pVDZ basis sets to calculate the electronic structures and stabilization energies with the help of TURBOMOLE software. The intermolecular dispersion terms are calculated using two different numerical models as functions of (i) molecular dispersion and (ii) total dispersion by atomic polarizability. The model with total dispersion energy providing a good correlation with the binding energy of the cluster than molecular dispersion model. Success of this method, lead us to propose a novel numerical method based on the contribution by whole sets of atoms, which is able to determine the origin of C-H/π interaction

Computational Investigation on Adsorption and Activation of Atmospheric Pollutants CO, NO and SO on Small Cobalt Clusters

The adsorption of CO, NO and SO on cobalt clusters (Co2-7) were investigated using density functional theory. The adsorption energy supports efficient chemisorption of greenhouse gases on the cobalt clusters, with CO and NO forming one to three Co-C and Co-N bonds, respectively, the first being the most stable. The SO formed bidentate complexes with Co-S and Co-O bonds in ConSO structures, displaying notably high adsorption energy. The interactions between Con clusters and gas molecules (G) result in weakened bonds of CO, NO, and SO, evident through increased bond lengths, red-shifted frequencies, and lowered local vibrational force constants in ConG complexes. The results with Bond weakening and charge transfer from metal to gas molecules suggest strong catalytic potential for small cobalt clusters in activating gas molecules. The current research findings hold significance in the quest for efficient catalytic processes to capture and recycle gaseous pollutants, contributing to a sustainable future

A combined experimental and computational study on the deactivation of a photo-excited 2,2′-pyridylbenzimidazole–water complex via excited-state proton transfer

In this report, we present solvent assisted excited-state proton transfer coupled to the deactivation of a photo-excited 2,2′-pyridylbenzimidazole bound to a single water molecule. Experimentally, the mass-selected 1 : 1 complex was probed using two-colour resonant two-photon ionization (2C-R2PI) and UV-UV hole-burning (HB) spectroscopy in a supersonically jet-cooled molecular beam. Computationally, three structural isomers were identified as the normal, the tautomer and the proton transfer product of the PBI-H2O complex in the excited S1 state using B3LYP-D4/def2-TZVPP and ADC(2) (MP2)/cc-pVDZ levels of theory. The most stable form in the ground state, i.e., the normal form, was identified using the excitation spectrum in the 30 544 to 30 936 cm−1 region. The 2C-R2PI spectrum showed a sudden break-off above the 000 + 392 cm−1 region, even though the Frack-Condon activity of the S1 ← S0 transition was measured beyond 000 + 1000 cm−1 in the HB spectrum. The intensity of the bands associated with the excited state intermolecular vibrational modes near the break-off region was found to be drastically decreased, which indicates efficient quantum mechanical tunnelling along the hydrogen transfer coordinate. The sudden disappearance of the intermolecular vibrational modes in the spectrum revealed the existence of a deactivation channel in the PBI-H2O complex near 392-450 cm−1 above the 000 transition. The computational investigation predicted that the deactivation of the excited-state occurred via the intersection between the S1 and S0 states, which was associated with the proton transfer from the H2O to the PBI molecule along the O(3)-H(4)→N(5) coordinate. The highest energy structure was identified as the point of intersection between the nπ* (S2) and ππ* (S1) states. The associated barrier height was experimentally determined to be 392-450 cm−1, which showed a reasonable agreement with the calculated excited-state proton transfer barrier. Competing reaction channels such as dissociation and tautomerization were found to be highly energetically inaccessible. © 2022 The Royal Society of Chemistr

Theoretical Investigation of C9H9 Radicals: A Key Combustion Intermediate and A Potential Interstellar Molecule

Density functional theory has been used to investigate the geometries, vibrational frequencies, rotational constants and ionisation potential of C9H9 radicals. Vertical electronic transition energies of C9H9 radicals are calculated by using time-dependent density functional theory. The adiabatic excitation energies and frequency calculations in excited state of C9H9 radicals have been done using DFT. Present results show that the most stable structure of C9H9 radicals is 1-indanyl radical. The adiabatic excitation energies and frequency calculations in excited state of 7 stable isomers (1-indanyl, 2-indanyl, 1-phenylallyl, 2-phenylallyl, 4-vinylbenzyl, 3-vinylbenzyl, 2-vinylbenzyl radical) of C9H9 radicals have been done. The computationally calculated vertical and adiabatic excitation energies of these 7 isomers are in good agreements with experimental observations. The high-resolution spectra of experimental R2C2PI spectrum at 618.2 nm and 601.4 nm have good matching with FCF data of 4-vinylbenzyl radical and 3-vinylbenzyl radical respectively. On the basis of the present calculations and results 4-vinylbenzyl and 3-vinylbenzyl radical of C9H9 radicals are most likely the carrier of the experimental R2C2PI spectra. These are the potential DIB carrier towards HD183143 and HD204827