Recasting the wobbling-in-a-cone model for the rotational anisotropy of phenylselenocyanate in poly(methyl methacrylate): Effect of internal bond rotation and polymer segmental motion.

The rotational anisotropy of a molecule in a constrained environment is modeled by wobbling-in-a-cone (WIAC) motion, which describes the angular space sampled by the molecule. Recent polarization-selective IR pump-probe measurements have applied this model to phenylselenocyanate in amorphous polymers, aiming to probe the surrounding free volume. A faster rotational timescale was hypothesized to reflect the angular space within the static voids of the polymer matrix, while a slower timescale relates to constraint release by the polymer backbones.

Construction of N-Rich Aminal-Linked Porous Organic Polymers for Outstanding Precombustion CO Capture and H Purification: A Combined Experimental and Theoretical Study.

A large number of scientific investigations are needed for developing a sustainable solid sorbent material for precombustion CO capture in the integrated gasification combined cycle (IGCC) that is accountable for the industrial coproduction of hydrogen and electricity. Keeping in mind the industrially relevant conditions (high pressure, high temperature, and humidity) as well as good CO/H selectivity, we explored a series of sorbent materials. An all-rounder player in this game is the porous organic polymers (POPs) that are thermally and chemically stable, easily scalable, and precisely tunable.

Charge-Shifted Weak Noncovalent Interactions in the Atmospherically Important OCS Microhydrates.

Stratospheric aerosol, mainly comprising microhydrated carbonyl sulfide (OCS), is among the primary drivers of climate change. In this study, we investigate the effect of microhydration on the structure, energetics, and vibrational properties of the neutral OCS molecule using ab initio calculation, molecular electrostatic potential (MESP), topological analyses of electron density, and natural bond orbital (NBO) analyses. The complexation energy increases with the cluster size, and the first solvation shell of OCS consists of four water molecules that interact with the OCS moiety preferentially through S···O, O···O, and C···O type of weak noncovalent interaction instead of the typical O···H-O and S···H-O H-bonds.

Dual active sites in a triazine-based covalent organic polymeric framework promoting oxygen reduction reaction.

A new significant feature of a triazine-based covalent organic polymer electrocatalyst is demonstrated. The metal-free electrocatalyst has dual-active sites, which enable it to entangle oxygen a push-pull interaction that plays a crucial role in promoting the oxygen reduction reaction.

Metal-Free Pyrene-Based Conjugated Microporous Polymer Catalyst Bearing N- and S-Sites for Photoelectrochemical Oxygen Evolution Reaction.

The development of an efficient, sustainable, and inexpensive metal-free catalyst for oxygen evolution reaction (OER) photoelectrochemical water splitting is very demanding for energy conversion processes such as green fuel generators, fuel cells, and metal-air batteries. Herein, we have developed a metal-free pyrene-based nitrogen and sulfur containing conjugated microporous polymer having a high Brunauer-Emmett-Teller surface area (761 m g) and a low bandgap of 2.09 eV for oxygen evolution reaction (OER) in alkaline solution.

Correction: Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(II) from polluted water.

Correction for 'Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(II) from polluted water' by Asim Baumik , , 2020, , 3963-3966, DOI 10.1039/D0CC00407C.

Adsorbed Water Structure on Acrylate-Based Biocompatible Polymer Surface.

The role of water in the excellent biocompatibility of the acrylate-based polymers widely used for antibiofouling coating material has been realized previously. Here, we report femtosecond mid-infrared pump-probe spectroscopy of the OD stretch band of HOD molecule adsorbed on highly biocompatible poly(2-methoxyethyl) acrylate [PMEA] and poorly biocompatible poly(2-phenoxyethyl) acrylate [PPEA], both of which reveal that there are two water species with significantly different vibrational lifetime. PMEA interacts more strongly with water than PPEA through the H-bonding interaction between carbonyl (C═O) and water.

Effect of isotope substitution on the Fermi resonance and vibrational lifetime of unnatural amino acids modified with IR probe: A 2D-IR and pump-probe study of 4-azido-L-phenyl alanine.

The infrared (IR) probe often suffers from an unexpected complex absorption profile due to the Fermi resonance and short vibrational lifetime, which restricts the application of time-resolved IR spectroscopy to investigate the site-specific structural dynamics of the protein. Researchers have found that isotope substitution to the IR probe not only removes the Fermi resonance but also extends the dynamic observation window with a prolonged vibrational lifetime. This method has been successfully applied to modify the vibrational properties of many IR probes for time-resolved spectroscopy and imaging.

Two-dimensional IR spectroscopy reveals a hidden Fermi resonance band in the azido stretch spectrum of β-azidoalanine.

Azido stretch modes in a variety of azido-derivatized nonnatural amino acids and nucleotides have been used as a site-specific infrared (IR) probe for monitoring changes in their conformations and local electrostatic environments. The vibrational bands of azide probes are often accompanied by complex line shapes with shoulder peaks, which may arise either from incomplete background subtraction, Fermi resonance, or multiple conformers. The isotope substitution in the infrared probe has thus been introduced to remove Fermi resonances without causing a significant perturbation to the structure.

Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(ii) from polluted water.

A new N- and S-rich highly ordered periodic mesoporous organosilica material DMTZ-PMO bearing thiadiazole and thiol moieties inside the pore-wall of a 2D-hexagonal nanomaterial has been synthesized. DMTZ-PMO shows a very high surface area (971 m g), and can be used for efficient and fast removal of Hg from polluted water with a very high Hg uptake capacity of 2081 mg g.

Solvent organization around the noncanonical part of tyrosine modulates its fluorescence properties.

Noncanonical amino acids are important molecules that enhance the functionality of proteins, and they are also intensively used in therapeutics. In this paper, we have investigated the fluorescence properties of the noncanonical amino acid 2-(trifluoromethyl) tyrosine (TFTyr) in three different alcohols, namely ethanol (ETH), monofluoroethanol (MFE), and trifluoroethanol (TFE), using spectroscopy, quantum chemical calculations and MD simulations. Further, we have compared its fluorescence properties with those of its canonical derivative tyrosine (Tyr) in the same solvents to understand the role of the noncanonical -CF3 group in the fluorescence properties of TFTyr.

Role of Surface Phenolic-OH Groups in N-Rich Porous Organic Polymers for Enhancing the CO Uptake and CO/N Selectivity: Experimental and Computational Studies.

Design and successful synthesis of phenolic-OH and amine-functionalized porous organic polymers as adsorbent for postcombustion CO uptake from flue gas mixtures along with high CO/N selectivity is a very demanding research area in the context of developing a suitable adsorbent to mitigate greenhouse gases. Herein, we report three triazine-based porous organic polymers TrzPOP-1, -2, and -3 through the polycondensation of two triazine rings containing tetraamine and three dialdehydes. These porous organic polymers possess high Brunauer-Emmett-Teller (BET) surface areas of 995, 868, and 772 m g, respectively.

Understanding the Role of Hydrophobic Terminal in the Hydrogen Bond Network of the Aqueous Mixture of 2,2,2-Trifluoroethanol: IR, Molecular Dynamics, Quantum Chemical as Well as Atoms in Molecules Studies.

The aqueous mixture of 2,2,2-trifluoroethanol (TFE) is one of the important alcoholic solvents which has been extensively used for understanding the stability of proteins as well as several chemical reactions. In this paper, the deconvolution of the IR lines in the OH-stretching region has been applied to understand the local structure of water-water, alcohol-water, and alcohol-alcohol interactions in the water mixture of TFE and ethanol (ETH). Further, molecular dynamics simulations, quantum chemical calculations, and atoms in molecules analysis have been performed to encode the local structure information obtained from the experimental data.

Hydrophobic fluorine mediated switching of the hydrogen bonding site as well as orientation of water molecules in the aqueous mixture of monofluoroethanol: IR, molecular dynamics and quantum chemical studies.

The local structures between water-water, alcohol-water and alcohol-alcohol have been investigated for aqueous mixtures of ethanol (ETH) and monofluoroethanol (MFE) by the deconvolution of IR bands in the OH stretching region, molecular dynamics simulation and quantum chemical calculations. It has been found that the addition of a small amount of ETH into the aqueous medium increases the strength of the hydrogen bonds between water molecules. In an aqueous mixture of MFE, the substitution of a single fluorine induces a change in the orientation as well as the hydrogen bonding site of water molecules from the oxygen to the fluorine terminal of MFE.

Role of Dispersive Fluorous Interaction in the Solvation Dynamics of the Perfluoro Group Containing Molecules.

Perfluoro group containing molecules possess an important self-aggregation property through the fluorous (F···F) interaction which makes them useful for diverse applications such as medicinal chemistry, separation techniques, polymer technology, and biology. In this article, we have investigated the solvation dynamics of coumarin-153 (C153) and coumarin-6H (C6H) in ethanol (ETH), 2-fluoroethanol (MFE), and 2,2,2-trifluoroethanol (TFE) using the femtosecond upconversion technique and molecular dynamics (MD) simulation to understand the role of fluorous interaction between the solute and solvent molecules in the solvation dynamics of perfluoro group containing molecules. The femtosecond upconversion data show that the time scales of solvation dynamics of C6H in ETH, MFE, and TFE are approximately the same whereas the solvation dynamics of C153 in TFE is slow as compared to that of ETH and MFE.

Combined Molecular Dynamics, Atoms in Molecules, and IR Studies of the Bulk Monofluoroethanol and Bulk Ethanol To Understand the Role of Organic Fluorine in the Hydrogen Bond Network.

The presence of the fluorocarbon group in fluorinated alcohols makes them an important class of molecules that have diverse applications in the field of separation techniques, synthetic chemistry, polymer industry, and biology. In this paper, we have performed the density function theory calculation along with atom in molecule analysis, molecular dynamics simulation, and IR measurements of bulk monofluoroethanol (MFE) and compared them with the data for bulk ethanol (ETH) to understand the effect of the fluorocarbon group in the structure and the hydrogen bond network of bulk MFE. It has been found that the intramolecular O-H···F hydrogen bond is almost absent in bulk MFE.

Solvent organization around the perfluoro group of coumarin 153 governs its photophysical properties: An experimental and simulation study of coumarin dyes in ethanol as well as fluorinated ethanol solvents.

The self-aggregation property of the perfluoro group containing molecules makes it important in the research fields of biology and polymer and organic synthesis. In the quest of understanding the role of the perfluoro group on the photophysical properties of perfluoro-containing molecules in biologically important fluoroethanol solvents, we have applied photophysical as well as molecular dynamics simulation techniques to explore the properties of perfluoro groups containing molecule coumarin-153 (C153) in ethanol (ETH), monofluoroethanol (MFE), difluoroethanol (DFE), and trifluoroethanol (TFE) and compared them with the molecules without perfluoro moiety, namely coumarin-6H (C6H) and coumarin-480 (C480). In contrast to C6H and C480, the excited state lifetime of C153 in fluorinated ETHs is not monotonic.

Theoretical study on the microhydration of atmospherically important carbonyl sulfide in its neutral and anionic forms: bridging the gap between the bulk and finite size microhydrated cluster.

Carbonyl sulfide (OCS) is the most abundant and stable sulfur-containing triatomic gas present in the atmosphere that plays an important role in aerosol formation. Structure, energetics, and photoelectron spectral properties of the microhydrated OCS in its neutral and anionic forms have been studied by using the BP86, B3LYP, and MP2 methods. OCS is linear in the neutral state but bent in the anionic state.