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The rotational dynamics of isocyanogen (CNCN) is studied for its collision with para (p-) and ortho (o-) hydrogen (H2) in the temperature range of 1–100 K. These temperatures correspond to the cold dense molecular clouds in the interstellar medium where molecular hydrogen is the primary collider. An ab initio 4D potential energy surface (PES) is constructed keeping the two molecules under rigid rotor approximation. The PES is generated using the CCSD(T)-F12b/AVTZ level of theory. The 4D PES is further fitted into a neural network (NN) model, which can augment the surface and account for missing data points within spectroscopic accuracy. This NN-fitted PES is then expanded over a bispherical harmonics function to get radial terms, which are expressed into analytic functions. Thereafter, the cross sections (σ) are computed for rotational transitions of CNCN (j → j′) using the close-coupling and centrifugal sudden methods for both p-H2 (jc = 0) and o-H2 (jc = 1) collision till 194 cm−1. In addition, p-H2 (jc = 0, 2) cross sections are also computed using the centrifugal sudden approximation method. The collisional rates are achieved by taking the Boltzmann distribution of σ over the translational energy of H2 till 100 K. Finally, the CNCN–H2 rates are compared to CNCN–He and NCCN–H2 collisional rates. Comparing even and odd transitions for the CNCN–H2 rates show a propensity toward higher rates for even transitions especially for o-H2 collisions considering low-order transitions. [ABSTRACT FROM AUTHOR]

Phosphorous species are of great interest in interstellar chemistry since they are the basic blocks for building life here on Earth. Modelling the abundance and environment of recently detected PO |$^{+}$| under non-local thermodynamic equilibrium (LTE) requires rotational spectra of the molecule along with accurate collisional rates with the most abundant species, hydrogen and helium. A new 4D ab initio potential energy surface (PES) of PO |$^{+}$| – H |$_{2}$| collision is calculated using CCSD(T)/CBS(DTQ) methodology considering rigid rotor approximation. The region containing the minima of the PES is augmented using neural networks (NNs) model while very high potentials (⁠|$\gt 2500$| cm |$^{-1}$| ) and asymptotic region have been approximated using Slater and R |$^{-4}$| functions, respectively. The close coupling calculations have been performed using molscat software for both ortho and para -H |$_{2}$| . The rate coefficients have been reported for transitions |$j-j^{\prime }=$| |$1-0$|⁠ , |$2-1$|⁠ , |$3-2$|⁠ , and |$5-4$| through which PO |$^{+}$| has been experimentally detected in interstellar medium (ISM). The rate coefficients for even and odd transitions of PO |$^{+}$| with para -H |$_{2}$| are compared with that of helium and are found to be 1.1–2.0 times higher. For even transitions (|$\Delta j = 2$|), the ortho -H |$_{2}$| rates are 10 per cent higher than para -H |$_{2}$| rates. However, the trend reverses in the case of odd transitions (|$\Delta j = 1$|) when higher J transitions are considered at low temperatures. At higher temperatures, the ortho rates cross the para -H |$_{2}$| rates and become larger than the latter. The new rate coefficients with both ortho and para -H |$_{2}$| will enable accurate modelling of the PO |$^{+}$| abundance in the ISM under non-LTE conditions. [ABSTRACT FROM AUTHOR]

The rotational excitation rates of NCCN species are studied for its collision with hydrogen (H2) in temperatures ranging from 1 to 100 K. Such collisions can occur in the interstellar medium with H2 in either para (p-) or ortho (o-) state, of which the p-H2 state can be approximated via its collision with He (using a scaling factor) or with a reduced rigid rotor-H2 surface (by averaging over various orientations of H2). In the current work, a four-dimensional (4D) ab initio potential energy surface (PES) is considered to study the collision dynamics of H2 in both p- and o-states and the results are compared with previous approximations. The 4D surface is constructed using the explicitly correlated coupled-cluster method CCSD(T)-F12b with the augmented triple zeta basis AVTZ and then fitted into an artificial neural networks (NN) model to augment the surface and account for missing data points. The radial coefficients are obtained from this NN fitted 4D PES via a least square fit over two spherical harmonics functions. The cross sections (σ) are computed using the close-coupling (CC) method (until 230 cm−1) for both p- and o-H2 collisions, and the rates are obtained by Boltzmann distribution over the translational energy of H2 until 100 K. The o-H2 rates are found to be higher by 25%–30% and 10%–20% compared to the p-H2 rates for Δj = 2 and higher order transitions, respectively. The coupled-state/centrifugal sudden approximated rates are also computed and found to have deviations as large as 40% when compared to CC rates, thus making quantitative descriptions unreliable. [ABSTRACT FROM AUTHOR]

Photoredox catalysis provides a green and sustainable alternative for C−H activation of organic molecules that eludes harsh conditions and use of transition metals. The photocatalytic C−N borylation and C−H arylation mostly depend on the ruthenium and iridium complexes or eosin Y and the use of porphyrin catalysts is still in infancy. A series of novel 21‐thiaporphyrins (A2B2 and A3B type) were synthesized having carbazole/phenothiazine moieties at their meso‐positions and screened as catalysts for C−N borylation and C−H arylation. This paper demonstrates the 21‐thiaporphyrin catalyzed C−N borylation and het‐arylation of anilines under visible light. The method utilizes only 0.1 mol % of 21‐thiaporphyrin catalyst under blue light for the direct C−N borylation and het‐arylation reactions. A variety of substituted anilines were used as source for expensive and unstable aryl diazonium salts in the reactions. The heterobiaryls and aryl boronic esters were obtained in decent yields (up to 88 %). Versatility of the 21‐thiaporphyrin catalyst was tested by thiolation and selenylation of anilines under similar conditions. Mechanistic insight was obtained from DFT studies, suggesting that 21‐thiaporphyrin undergo an oxidative quenching pathway. The photoredox process catalyzed by 21‐thiaporphyrins offers a mild, efficient and metal‐free alternative for the formation of C−C, C−S, and C−Se bonds in aryl compounds; it can also be extended to borylation reaction. [ABSTRACT FROM AUTHOR]

In recent years, hydrogen (H2) has become the most sought-after sustainable energy carrier by virtue of its high energy content and carbon-free emission. The practical implementation of hydrogen as an alternative fuel calls for an efficient and secure storage medium. Within this framework, we have investigated Li-grafted Si-doped γ-graphyne for H2 storage applications by implementing the cutting-edge density functional theory (DFT). A dynamically and thermally stable Si-doped γ-graphyne (SiG) monolayer is functionalized with Li metal atoms that augmented the hydrogen binding strength of the nanolayer by almost three times, owing to the polarization effect of the Li atoms. The Li metal atoms get adsorbed over the monolayer, allowing a binding energy of −2.73 eV that is greater than the Li cohesive energy (−1.63 eV), which eliminates the metal–metal clustering probability. The reliability of the Li-functionalized SiG monolayer (Li8SiG) at elevated temperature has been further substantiated by performing and analyzing ab initio molecular dynamics (AIMD) simulations at 400 K. It is noteworthy that a total of four H2 molecules are held up by each Li atom with an average adsorption energy of −0.32 eV and a maximum gravimetric capacity of 8.48 wt%, which remarkably follows the US-DOE parameters. Partial density of states and Hirshfeld charge analysis are utilized to recognize the interaction channel which reveals the Kubas and Niu–Rao–Jena-like bonding among the metal atoms and loaded hydrogen molecules. The hydrogen occupancy calculated at different temperatures and pressures indicates that hydrogen molecules can be reversibly stored over the Li8SiG system, and it is noted that adsorbed H2 begins to desorb at 280 K, with complete desorption at 400 K and 20 atm (or lower). AIMD simulations are further performed to authenticate the H2 desorption at various temperatures, which agrees well with the occupation number analysis. All the outcomes advocate for efficient reversible hydrogen storage over the proposed host material. [ABSTRACT FROM AUTHOR]

A new four dimensional (4D) ab initio potential energy surface (PES) is generated for the collision of C4(3Σg−) with H2(1Σg), considering both molecules as rigid rotors. A supervised neural network model is created to augment the ab initio PES and to get the missing data points. Furthermore, space fixed expansion of the augmented PES is carried out using a least squares fit over two spherical harmonics terms, resulting in radial coefficients (λ1, λ2, and λ). The centre of symmetry in both C4 and H2 forces λ1 and λ2 to have even values, respectively. Moreover, the rotational states of C4 are only populated by odd levels due to its ground state triplet symmetry and the nuclear spin (I = 0) of 12C. The cross-sections and rate coefficients with para and ortho H2 partners are studied for various odd state transitions, where the rate coefficients of the ortho are 10–20% higher than those of the latter. The de-excitation rates obtained by the para H2 collisions are also compared to those of He and are found to be ∼1.7–2.8 times the He rates, across various order transitions. The simple scaling of He rates using a factor of 1.38 proves insufficient to describe para H2 rates. Therefore, these results show the importance of explicitly studying H2 as an important colliding partner, governing the kinetics of various rotational processes in the interstellar space. [ABSTRACT FROM AUTHOR]

The effect of para -hydrogen (j p = 0) collisions on the rotational de-excitation transitions of molecule NCCP is investigated in this study. The scattering information is obtained by spherically averaging a four-dimensional potential energy surface (4DPES) over various H2 molecule orientations. The calculations used the CCSD(T)-F12a method and aug-cc-pVTZ basis set to generate a 4DPES for the NCCP–H2 van der Waals system. Within the NCCP– para -H2 4DPES, a minimum energy point of 191.82 cm−1 is attained at a distance of 3.6 Å from the centre of mass of H2 and NCCP. To compute cross-sectional data for NCCP interacting with para -H2 (j p = 0), close coupling calculations are employed, encompassing total energies up to 600 cm−1. The resulting rate coefficients [ |$k_{j{\rightarrow }j^{\prime }}(T$|⁠)] are calculated across a temperature range spanning from 5 K to 200 K. In accordance with propensity, even Δ j = −2 transitions are highly preferred. Comparatively, the derived |$k_{j{\rightarrow }j^{\prime }}(T$|⁠) for NCCP–H2 are determined to be 1.5–4.5 times of NCCP–He. This observation implies that relying on a scaling factor of 1.38 to extrapolate rate coefficients for H2 collisions from those of NCCP–He is not a reliable approach. [ABSTRACT FROM AUTHOR]

The presence of inherent strain and electric field in the Janus transition metal dichalcogenide nanosheets widens their applications in nanodevices. The weak interactions between pristine Janus monolayers and gas molecules limit the applications of Janus sheets in gas sensing devices. However, tuning of structural and electronic properties by doping of foreign atoms in the lattice structure improves the gas sensing property of Janus WSSe monolayers. Herein, the superior gas sensing property of N, P, and As doped Janus WSSe monolayers for CO, NO, and HF gases has been studied using spin-polarized density functional theory. The binding energy analysis shows that the 3.12% doping of N, P, and As at S/Se sites is an exothermic process. New bands have been observed near the Fermi region in doped nanosheets. The simulations also reveal that doping improves the gas sensing properties of the doped sheets because of strong interactions between adsorbate and adsorbent. The interactions between gas molecules and doped WSSe monolayers are examined with the help of density of states plots. The uni-axial tensile strain tends to further improve the adsorption of CO on the nitrogen-doped WSSe nanosheet. Based on the present studies, it is evident that only 3.12% doping of foreign atoms makes WSSe Janus monolayers efficient material for CO, NO, and HF gas sensing without imposing external strain. [ABSTRACT FROM AUTHOR]

The objective of this study is to enhance our understanding of the existence of molecules in interstellar space by determining the collisional rate coefficients with the most prevalent species. The study examines the impact of para-H2 collisions, specifically when it is in its ground vibrational state with a nuclear spin of para-H2, i.e., jp = 0, on causing the rotational deexcitation of the diisocyanogen (CNNC) molecule. These scattering data are obtained as a result of spherically averaging a four-dimensional potential energy surface (4DPES) over the H2 orientations. Using the CCSD(T)-F12a approach and aug-cc-pVTZ basis sets, the ab initio 4DPES for the CNNC–H2 van der Waals system is calculated. The CNNC–para-H2 4DPES attains a global minimum of 221.38 cm−1 at the CNNC and H2 center of mass distance (R) of 3.1 Å. The method of close coupling calculations is employed for the purpose of calculating the cross-sectional data of CNNC with para-H2 (jp = 0), for total energies up to 1000 cm−1. Rate coefficients are computed over the temperature range of 1 K to 100 K. Propensity suggests that even Δj transitions are strongly preferred. The rate coefficients for CNNC–H2 are determined to be 0.90–2.95 times those of CNNC–He, which implies it is not reliable to estimate the H2 rate coefficients by multiplying the rate coefficients for CNNC–He collision with a scaling factor of 1.38. [ABSTRACT FROM AUTHOR]

Finding an ideal bioorthogonal reaction that responds to a wide range of biological queries and applications is of great interest in biomedical applications. Rapid diazaborine (DAB) formation in water by the reactions of ortho‐carbonyl phenylboronic acid with α‐nucleophiles is an attractive conjugation module. Nevertheless, these conjugation reactions demand to satisfy stringent criteria for bioorthogonal applications. Here we show that widely used sulfonyl hydrazide (SHz) offers a stable DAB conjugate by combining with ortho‐carbonyl phenylboronic acid at physiological pH, competent for an optimal biorthogonal reaction. Remarkably, the reaction conversion is quantitative and rapid (k2>103 M−1 s−1) at low micromolar concentrations, and it preserves comparable efficacy in a complex biological milieu. DFT calculations support that SHz facilitates DAB formation via the most stable hydrazone intermediate and the lowest energy transition state compared to other biocompatible α‐nucleophiles. This conjugation is extremely efficient on living cell surfaces, enabling compelling pretargeted imaging and peptide delivery. We anticipate this work will permit addressing a wide range of cell biology queries and drug discovery platforms exploiting commercially available sulfonyl hydrazide fluorophores and derivatives. [ABSTRACT FROM AUTHOR]

We present the detailed comparative study of dihydrogen adsorption in Li, Mg, Ca, and Sc decorated γ -graphyne (G γ) performed with density functional theory calculations. Hydrogen molecules are sequentially loaded onto metal decorated G γ. Maximum hydrogen weight percentage for Li, Mg, Ca, and Sc decorated G γ is found to be 8.69, 7.73, 8.10, and 6.83, respectively, with maximum 8 H 2 on Li, Mg, and Sc while 10 on Ca decorated G γ. All hydrogen molecules are physisorbed over all the complexes except that the first one on each Sc of G γ -2Sc is chemisorbed. Orbital hybridization involved in Dewar coordination of metal decoration and the Kubas mechanism of hydrogen adsorption has been explained with the partial density of states. Lower values of adsorption and desorption energies in these complexes indicate the reversibility of adsorption. These complexes obey high hardness and low electrophilicity principles and contain no imaginary frequencies which specify their stability. In Born-Oppenheimer molecular dynamics, reversibility of adsorption is proven at various temperatures. Based on the comparative studies of hydrogen weight percentage, energetics, stability, and reversibility, G γ -2Ca is proven to be a better hydrogen storage candidate. This comprehensive study confirms the potential of metal decorated γ -graphyne as a suitable hydrogen storage material. [ABSTRACT FROM AUTHOR]

Quantum dynamics of the molecule cyanogen (NCCN) and its collision with helium taking place in the interstellar medium has been studied. An ab initio potential energy surface of NCCN—He, a van der Waals complex, is generated using the high-level single reference coupled-cluster with single and double and perturbative triple excitation method and aug-cc-pVQZ basis sets. Using the multipole expansion, Legendre coefficients have been calculated and utilized in determining collisional cross sections. Close-coupling calculations have been performed to study rotational excitations for He collision with NCCN. Due to nuclear spin statistics, collision induced transitions have even Δj, while odd Δj transitions are forbidden. The presence of resonances arising from rapid oscillation of cross sections in the low energy region is the result of quasi-bound states in the NCCN—He van der Waals complex. Among all the transitions, Δj = 2 are found to be predominant for excitation. Thereafter, for each transition, the rate coefficients have been calculated which decrease with increasing values of j and Δj. The result of this work will be helpful to accurately model the abundance of cyanogen in stellar atmospheres and interstellar gas. [ABSTRACT FROM AUTHOR]

In this article, we report band structure studies of zigzag graphene nanoribbons (ZGNRs) on introducing defects (sp3 hybridized carbon atoms) in different concentrations at edges by varying the ratio of sp3 to sp2 hybridized carbon atoms. On the basis of theoretical analyses, bandgap values of ZGNRs are found to be strongly dependent on the relative arrangement of sp3 to sp2 hybridized carbon atoms at the edges for a defect concentration; so the findings would greatly help in understanding the bandgap of nanoribbons for their electronic applications. [ABSTRACT FROM AUTHOR]

NCCP, a phosphorous species, is believed to have been discovered in the carbon-rich star IRC+10216. Understanding collisional properties, such as cross-sections (⁠|$\sigma _{j\rightarrow j^{\prime }}$|⁠) and rate coefficients (⁠|$k_{j\rightarrow j^{\prime }}$|⁠), is important for the reliable determination of molecular abundance. The non-reactive collisions between NCCP and He species at low temperatures are the subject of this study. Calculations are based on new ab initio potential energy surface (PES) of NCCP–He. The PES calculations are carried out at the CCSD(T)–F12a in conjunction with the aug-cc-pVTZ basis set. The PES is found to have a global minimum towards the N end with a well depth of −46.40 cm−1. The ab initio points are analytically fitted on to the Legendre polynomial relevant for quantum scattering. From this fitted PES, the integral inelastic rotational cross-sections of NCCP with He collisions are computed for total energies up to 550 cm−1, using the accurate close coupling approach of quantum mechanics. The resonances are observed at low total energies due to quasi-bound states of the NCCP−He complex. Rate coefficients are determined among the 19 lowest rotational levels of NCCP by thermally averaging the cross-sections at low temperatures. The de-excitation rate coefficients increase with decreasing Δ j. [ABSTRACT FROM AUTHOR]

Li-ion batteries are one of the sustainable alternatives to meet the growing energy demands of an increasing population. However, finding a suitable negative electrode is key for improving battery performance. In the present work, first principles-based investigations are carried out to explore the capability of a planar 2D C-silicyne nanosheet – which is a Si analogue of α-graphyne having –C≡C– substitution – as an anode for improving the performance of Li-ion batteries. Thermally and dynamically stable C-silicyne sheets exhibit a metallic nature as inferred from the density of states studies. The average adsorption energies for sequential adsorption of the Li atom over the monolayer range from −1.35 to −0.46 eV, implying favourable interactions between the monolayer and the Li atom which indicate that during the lithiation process, clustering amongst the metal atoms is not preferred. The energy barrier for the migration of Li-ions is 0.21 eV, indicating an active charge/discharge process. A high storage capacity of 836.07 mA h g−1 and a working potential of 0.60 V is obtained. A negligible amount of volume change of the C-silicyne monolayer after full lithiation is observed which implies good cyclability. All these outcomes imply that C-silicyne nanosheets are a potential anode material for next-generation LIBs. [ABSTRACT FROM AUTHOR]

Transition‐metal‐free photoredox catalysis was used for C−N borylation and C−H arylation with 0.1 mol % loading of 21‐thiaporphyrin. Under blue light, a thiaporphyrin catalyst was employed for the synthesis of boronic esters and hetero‐biaryl moieties having furan, thiophene or pyrrole. The methodology was also extended to synthesize diphenyl selenide and diphenyl sulfide derivatives. More information can be found in the Research Article by I. Gupta and co‐workers (DOI: 10.1002/chem.202401623)...By Anu Janaagal; Apoorv Kushwaha; Pranjali Jhaldiyal; T. J. Dhilip Kumar and Iti GuptaReported by Author; Author; Author; Author; Author [Extracted from the article]

Heteroatom doping into 2-dimensional lattices of materials such as graphene brings revolutionary reform in the field of materials endowing the parent material with remarkable properties. Herein, a state-of-the-art 2-dimensional carbon lattice doped by Si atoms, Si doped T-graphene (t-SiC3), has been reported and its application as an anode electrode material in secondary Na ion batteries has been demonstrated. A detailed theoretical investigation following density functional theory establishes the geometric, physical, and chemical domains of the monolayer. The metallic nature of the monolayer verified by the density of states adds up to its advantage of being used as the electrode. Moreover, efficient adsorption in addition to easy diffusion emphasizes the high rate kinetics of the monolayer. Efficient charge redistribution is achieved signifying energetically stable adsorption of Na ions during the electrochemical half cell cycle. For practical realization, an efficient storage capacity of 686 mA h g−1 along with a lower energy barrier of 0.3 eV for Na ion diffusion is obtained. Further, the average voltage of 0.2 V calculated for t-SiC3 renders its efficacy to be used as an anode material in reversible Na ion batteries. The properties underlying t-SiC3 extend its potential for a wide spectrum of applications. [ABSTRACT FROM AUTHOR]

The quantum dynamics of rotational transitions of the diisocyanogen (CNNC) molecule undergoing collision with the helium (He) atom occurring in the interstellar medium (ISM) has been studied. The rotational deexcitation cross sections are extracted by first computing an ab initio potential energy surface of CNNC—He using the coupled-cluster with single and double and perturbative triple excitations with the F12a method (CCSD(T)-F12a) employing the aug-cc-pVTZ basis set. Utilizing the multipole expansions, collisional cross sections are determined for total energies of up to 1000 cm−1 by the close coupling equations. The discussion on propensity rules suggests that the transitions have even Δj values, while odd Δj valued transitions are forbidden due to C and N nuclei spin statistics. Quasi-bound states present in the CNNC—He van der Waals complex resulted in the resonances coming from the rapid oscillations in the values of the cross sections in the region of low energy. Rotational deexcitation rate coefficients are further worked out by averaging the calculated cross sections at temperatures below 200 K. The new findings of the study will be beneficial in modeling the abundance of diisocyanogen in the ISM. [ABSTRACT FROM AUTHOR]

With the depleting resources of energy and increasing demand, the need for sustainable and renewable energy resources has become the need of the hour. The low storage capacity of current materials for Na/K ion batteries has led to the quest to identify suitable materials for an electrode with excellent electrochemical properties. In the present work, a systematic theoretical investigation of C-silicyne, a planar 2-dimensional hexagonal lattice, is performed to establish the geometric and thermal properties and stability. The electronic properties illustrate the metallic nature of C-silicyne, which is conserved even after the effective adsorption of Na/K ions on the surface of the monolayer. For the practical functionality, the storage capacity of C-silicyne is evaluated as 591 mA h g−1 for Na ions and 443 mA h g−1 for K ions. Moreover, the low diffusion barriers for the Na (0.57 eV) and K (0.34 eV) ions display their feasible movement across the monolayer as the electrochemical cycle progresses. The average working voltage is found to lie in the range of 0.1–1 V, which is required for the effective functioning of the anode in a Na/K ion battery. These results demonstrate the potential of C-silicyne as a material for the anode in Na/K ion batteries. [ABSTRACT FROM AUTHOR]

Hydrogen undergoes dissociative chemisorption on small titanium clusters. How the electronic structure of the cluster changes as a function of the number of adsorbed hydrogen atoms is an important issue in nanocatalysis and hydrogen storage. In this paper, a detailed theoretical investigation of the structural, energetic, and electronic properties of the icosahedral Ti13 cluster is presented as a function of the number of adsorbed hydrogen atoms. The results show that hydrogen loaded Ti13H20 and Ti13H30 clusters are exceptionally stable and are characterized by hydrogen multicenter bonds. In Ti13H20, the dissociated hydrogen atoms are bound to each of the 20 triangular faces of Ti13, while in Ti13H30, they are bound to the 30 Ti–Ti edges of Ti13. Consequently, the chemisorption and desorption energies of the Ti13H20 (1.93 eV, 3.10 eV) are higher than that of Ti13H30 (1.13 eV, 1.95 eV). While increased hydrogen adsorption leads to an elongation of the Ti–Ti bonds, there is a concomitant increase in the electrostatic interaction between the dissociated hydrogen atoms and the Ti13 cluster. This enhanced interaction results from the participation of the subsurface titanium atom at higher hydrogen concentrations. Illustrative results of hydrogen saturation on the larger icosahedral Ti55 cluster are also discussed. The importance of these results on hydrogen saturated titanium clusters in elucidating the mechanism of hydrogen adsorption and desorption in titanium doped complex metal hydrides is discussed. [ABSTRACT FROM AUTHOR]

Platinum is the most widely used catalyst in fuel cell electrodes. Designing improved catalysts with low or no platinum content is one of the grand challenges in fuel cell research. Here, we investigate electronic structures of Pt4 and Pt3Co clusters and report a comparative study of adsorption of H2, O2, and CO molecules on the two clusters using density functional theory. The adsorption studies show that H2 undergoes dissociative chemisorption on the tetrahedral clusters in head on and side on approaches at Pt centers. O2 dissociation occurs primarily in three and four center coordinations and CO prefers to adsorb on Pt or Co atop atoms. The adsorption energy of O2 is found to be higher for the Co doped cluster. For CO, the Pt atop orientation is preferred for both Pt4 and Pt3Co tetrahedral clusters. Adsorption of CO molecule on tetrahedral Pt3Co in side on approach leads to isomerization to planar rhombus geometry. An analysis of Hirshfeld charge distribution shows that the clusters become more polarized after adsorption of the molecules. [ABSTRACT FROM AUTHOR]

The authors have performed a systematic computational study of the hydrogen storage capacity of model organometallic compounds consisting of Sc, Ti, and V transition metal atoms bound to CmHm rings (m=4–6). For all the complexes considered, the hydrogen storage capacity is limited by the 18-electron rule. The maximum retrievable H2 uptake predicted is 9.3 wt % using ScC4H4, slightly better than the 9.1 wt % hydrogen using TiC4H4, and much larger than the ∼7 wt % hydrogen with VC4H4, where only four H2 molecules can be adsorbed. The kinetic stability of these hydrogen-covered organometallic complexes is reviewed in terms of the energy gap between the highest occupied and lowest unoccupied molecular orbitals and the strength and nature of successive H2 bindings. [ABSTRACT FROM AUTHOR]

Proton and hydrogen atom time-of-flight spectra in collision energy range of Etrans=9.5–30 eV show that the endoergic charge transfer process in the H++CO system is almost an order of magnitude less probable than the elastic scattering [G. Niedner-Schatteburg and J. P. Toennies, Adv. Chem. Phys. LXXXII, 553 (1992)]. Ab initio computations at the multireference configuration interaction level have been performed to obtain the ground- and several low-lying excited electronic state potential energy curves in three different molecular orientations namely, H+ approaching the O-end and the C-end (collinear), and H+ approaching the CO molecule in perpendicular configuration with fixed CO internuclear distance. Nonadiabatic coupling terms between the ground electronic state (H++CO) and the three low-lying excited electronic states (H+CO+) have been computed and the corresponding diabatic potentials have been obtained. A time-dependent wavepacket dynamics study is modeled first involving only the ground and the first excited states and then involving the ground and the three lowest excited states at the collision energy of 9.5 eV. The overall charge transfer probability have been found to be ≈20%–30% which is in qualitative agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

A bifunctional, microporous ZnII metal-organic framework, [Zn2(NH2BDC)2(dpNDI)] n (MOF 1) (where, NH2BDC=2-aminoterephthalic acid, dpNDI= N, N′-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF 1 shows an interesting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99×3.58 Å and 4.58×5.38 Å decorated with pendent −NH2 groups. Owing to the presence of a basic functionalized pore surface, MOF 1 exhibits selective adsorption of CO2 with high value of heat of adsorption ( Qst=46.5 kJ mol−1) which is further supported by theoretically calculated binding energy of 48.4 kJ mol−1. Interestingly, the value of Qst observed for MOF 1 is about 10 kJ mol−1 higher than that of analogues MOF with the benzene-1,4-dicarboxylic acid (BDC) ligand, which establishes the critical role of the −NH2 group for CO2 capture. Moreover, MOF 1 exhibits highly selective and sensitive sensing of the nitroaromatic compound (NAC), 2,4,6-trinitrophenol (TNP) over other competing NACs through a luminescence quenching mechanism. The observed selectivity for TNP over other nitrophenols has been correlated to stronger hydrogen bonding interaction of TNP with the basic −NH2 group of MOF 1, which is revealed from DFT calculations. To the best of our knowledge, MOF 1 is the first example of an interpenetrated ZnII-MOF exhibiting selective adsorption of CO2 as well as efficient aqueous-phase sensing of TNP; investigated through combined experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

In this article, we put forward a resolution to the prolonged ambiguity in energy band gaps between theory and experiments of fabricated graphene nanoribbons (GNRs). Band structure calculations using density functional theory are performed on oxygen-passivated GNR supercells of customized edge configurations without disturbing the inherent sp² hybridization of carbon atoms. Direct band gaps are observed for both zigzag and armchair GNRs, consistent with the experimental reports. In addition, we provide an explanation of the experimentally observed scattered band gap values of GNRs as a function of width in a crystallographic orientation on the basis of edge configurations. We conclude that edge configurations of GNRs significantly contribute to band gap formation in addition to its width for a given crystallographic orientation and will play a crucial role in band gap engineering of GNRs for future research on fabrication of nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Structures and physical properties of small palladium clusters Pdn up to n = 15 and several selected larger clusters were studied using density functional theory under the generalized gradient approximation. It was found that small Pdn clusters begin to grow 3-dimensionally at n = 4 and evolve into symmetric geometric configurations, such as icosahedral and fcc-like, near n = 15. Several isomers with nearly degenerate average binding energies were found to coexist and the physical properties of these clusters were calculated. For several selected isomers, relatively moderate energy barriers for structural interchange for a given cluster size were found, implying that isomerization could readily occur under ambient conditions. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

Photoredox catalysis provides a green and sustainable alternative for C-H activation of organic molecules that eludes harsh conditions and use of transition metals. The photocatalytic C-N borylation and C-H arylation mostly depend on the ruthenium and iridium complexes or eosin Y and the use of porphyrin catalysts is still in infancy. A series of novel 21-thiaporphyrins (A 2 B 2 and A 3 B type) were synthesized having carbazole/phenothiazine moieties at their meso-positions and screened as catalysts for C-N borylation and C-H arylation. This paper demonstrates the 21-thiaporphyrin catalyzed C-N borylation and het-arylation of anilines under visible light. The method utilizes only 0.1 mol % of 21-thiaporphyrin catalyst under blue light for the direct C-N borylation and het-arylation reactions. A variety of substituted anilines were used as source for expensive and unstable aryl diazonium salts in the reactions. The heterobiaryls and aryl boronic esters were obtained in decent yields (up to 88 %). Versatility of the 21-thiaporphyrin catalyst was tested by thiolation and selenylation of anilines under similar conditions. Mechanistic insight was obtained from DFT studies, suggesting that 21-thiaporphyrin undergo an oxidative quenching pathway. The photoredox process catalyzed by 21-thiaporphyrins offers a mild, efficient and metal-free alternative for the formation of C-C, C-S, and C-Se bonds in aryl compounds; it can also be extended to borylation reaction., (© 2024 Wiley-VCH GmbH.)

The rotational dynamics of isocyanogen (CNCN) is studied for its collision with para (p-) and ortho (o-) hydrogen (H2) in the temperature range of 1-100 K. These temperatures correspond to the cold dense molecular clouds in the interstellar medium where molecular hydrogen is the primary collider. An ab initio 4D potential energy surface (PES) is constructed keeping the two molecules under rigid rotor approximation. The PES is generated using the CCSD(T)-F12b/AVTZ level of theory. The 4D PES is further fitted into a neural network (NN) model, which can augment the surface and account for missing data points within spectroscopic accuracy. This NN-fitted PES is then expanded over a bispherical harmonics function to get radial terms, which are expressed into analytic functions. Thereafter, the cross sections (σ) are computed for rotational transitions of CNCN (j → j') using the close-coupling and centrifugal sudden methods for both p-H2 (jc = 0) and o-H2 (jc = 1) collision till 194 cm-1. In addition, p-H2 (jc = 0, 2) cross sections are also computed using the centrifugal sudden approximation method. The collisional rates are achieved by taking the Boltzmann distribution of σ over the translational energy of H2 till 100 K. Finally, the CNCN-H2 rates are compared to CNCN-He and NCCN-H2 collisional rates. Comparing even and odd transitions for the CNCN-H2 rates show a propensity toward higher rates for even transitions especially for o-H2 collisions considering low-order transitions., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

A new four dimensional (4D) ab initio potential energy surface (PES) is generated for the collision of C 4 ( 3 Σ g - ) with H 2 ( 1 Σ g ), considering both molecules as rigid rotors. A supervised neural network model is created to augment the ab initio PES and to get the missing data points. Furthermore, space fixed expansion of the augmented PES is carried out using a least squares fit over two spherical harmonics terms, resulting in radial coefficients ( λ 1 , λ 2 , and λ ). The centre of symmetry in both C 4 and H 2 forces λ 1 and λ 2 to have even values, respectively. Moreover, the rotational states of C 4 are only populated by odd levels due to its ground state triplet symmetry and the nuclear spin ( I = 0) of 12 C. The cross-sections and rate coefficients with para and ortho H 2 partners are studied for various odd state transitions, where the rate coefficients of the ortho are 10-20% higher than those of the latter. The de-excitation rates obtained by the para H 2 collisions are also compared to those of He and are found to be ∼1.7-2.8 times the He rates, across various order transitions. The simple scaling of He rates using a factor of 1.38 proves insufficient to describe para H 2 rates. Therefore, these results show the importance of explicitly studying H 2 as an important colliding partner, governing the kinetics of various rotational processes in the interstellar space.

The selective carbon capture and utilization (CCU) as a one-carbon (C1) feedstock offers dual advantages for mitigating the rising atmospheric CO 2 content and producing fine chemicals/fuels. In this context, herein, we report the application of a porous bipyridine-functionalized, pyrene-based covalent organic framework (Pybpy-COF) for the stable anchoring of catalytic Ag(0) nanoparticles (NPs) and its catalytic investigation for fixation of CO 2 to commodity chemicals at ambient conditions. Notably, Ag@Pybpy-COF showed excellent catalytic activity for the carboxylation of various terminal alkynes to corresponding alkynyl carboxylic acids/phenylpropiolic acids via C-H bond activation under atmospheric pressure conditions. Besides, carboxylative cyclization of various propargylic amines with CO 2 to generate 2-oxazolidinones, an important class of antibiotics, has also been achieved under mild conditions. This significant catalytic activity of Ag@Pybpy-COF with wide functional group tolerance is rendered by the presence of highly exposed, alkynophilic Ag(0) catalytic sites decorated on the pore walls of high surface area (787 m 2 g -1 ) Pybpy-COF. Further, density functional theory calculations unveiled the detailed mechanistic path of the Ag@Pybpy-COF-catalyzed transformation of CO 2 to alkynyl carboxylic acids and 2-oxazolidinones. Moreover, the catalyst showed high recyclability for several cycles of reuse without significant loss in its catalytic activity and structural rigidity. This work demonstrates the promising application of Pybpy-COF for stable anchoring of Ag NPs for successful transformation of CO 2 to valuable commodity chemicals at ambient conditions.

The objective of this study is to enhance our understanding of the existence of molecules in interstellar space by determining the collisional rate coefficients with the most prevalent species. The study examines the impact of para -H 2 collisions, specifically when it is in its ground vibrational state with a nuclear spin of para -H 2 , i.e. , j p orientations. Using the CCSD(T)-F12a approach and aug-cc-pVTZ basis sets, the 2 orientations. Using the CCSD(T)-F12a approach and aug-cc-pVTZ basis sets, the ab initio 4DPES for the CNNC-H 2 van der Waals system is calculated. The CNNC- para -H 2 4DPES attains a global minimum of 221.38 cm -1 at the CNNC and H 2 center of mass distance ( R ) of 3.1 Å. The method of close coupling calculations is employed for the purpose of calculating the cross-sectional data of CNNC with para -H 2 ( j p = 0), for total energies up to 1000 cm -1 . Rate coefficients are computed over the temperature range of 1 K to 100 K. Propensity suggests that even Δ j transitions are strongly preferred. The rate coefficients for CNNC-H 2 are determined to be 0.90-2.95 times those of CNNC-He, which implies it is not reliable to estimate the H 2 rate coefficients by multiplying the rate coefficients for CNNC-He collision with a scaling factor of 1.38.

The rotational excitation rates of NCCN species are studied for its collision with hydrogen (H2) in temperatures ranging from 1 to 100 K. Such collisions can occur in the interstellar medium with H2 in either para (p-) or ortho (o-) state, of which the p-H2 state can be approximated via its collision with He (using a scaling factor) or with a reduced rigid rotor-H2 surface (by averaging over various orientations of H2). In the current work, a four-dimensional (4D) ab initio potential energy surface (PES) is considered to study the collision dynamics of H2 in both p- and o-states and the results are compared with previous approximations. The 4D surface is constructed using the explicitly correlated coupled-cluster method CCSD(T)-F12b with the augmented triple zeta basis AVTZ and then fitted into an artificial neural networks (NN) model to augment the surface and account for missing data points. The radial coefficients are obtained from this NN fitted 4D PES via a least square fit over two spherical harmonics functions. The cross sections (σ) are computed using the close-coupling (CC) method (until 230 cm-1) for both p- and o-H2 collisions, and the rates are obtained by Boltzmann distribution over the translational energy of H2 until 100 K. The o-H2 rates are found to be higher by 25%-30% and 10%-20% compared to the p-H2 rates for Δj = 2 and higher order transitions, respectively. The coupled-state/centrifugal sudden approximated rates are also computed and found to have deviations as large as 40% when compared to CC rates, thus making quantitative descriptions unreliable., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

Finding an ideal bioorthogonal reaction that responds to a wide range of biological queries and applications is of great interest in biomedical applications. Rapid diazaborine (DAB) formation in water by the reactions of ortho-carbonyl phenylboronic acid with α-nucleophiles is an attractive conjugation module. Nevertheless, these conjugation reactions demand to satisfy stringent criteria for bioorthogonal applications. Here we show that widely used sulfonyl hydrazide (SHz) offers a stable DAB conjugate by combining with ortho-carbonyl phenylboronic acid at physiological pH, competent for an optimal biorthogonal reaction. Remarkably, the reaction conversion is quantitative and rapid (k 2 >10 3  M -1  s -1 ) at low micromolar concentrations, and it preserves comparable efficacy in a complex biological milieu. DFT calculations support that SHz facilitates DAB formation via the most stable hydrazone intermediate and the lowest energy transition state compared to other biocompatible α-nucleophiles. This conjugation is extremely efficient on living cell surfaces, enabling compelling pretargeted imaging and peptide delivery. We anticipate this work will permit addressing a wide range of cell biology queries and drug discovery platforms exploiting commercially available sulfonyl hydrazide fluorophores and derivatives., (© 2023 Wiley-VCH GmbH.)

Boron-pnictogen (BX; X = N, P, As, Sb) materials, in most cases, share structural characteristics with the aesthetically pleasing architectures of carbon allotropes. Recently, a two-dimensional (2D) metallic carbon allotrope (biphenylene) has been synthesized using experimental methods. In the present study, we have examined the structural stabilities, mechanical properties, and electronic fingerprints of biphenylene analogs of boron-pnictogen (bp-BX) monolayers using state-of-the-art electronic structure theory. We have validated the dynamical stability using phonon band dispersion analysis and thermal stabilities using ab initio molecular dynamics studies. The bp-BX monolayers exhibit a positive (bp-BN) and negative (bp-BP, bp-BAs, bp-BSb) Poisson's ratio with anisotropic mechanical properties in the 2D plane. Electronic structure studies unveil that the bp-BX monolayers show semiconducting properties with an energy gap of 4.50, 1.30, 2.28 and 1.24 eV for X = N, P, As and Sb, respectively. Computed band edge positions, lighter charge carriers and optimally separated hole and electron regions indicate that the bp-BX monolayers can serve as potential candidates for the metal-free water dissociation reaction using photocatalysis.

Lignin-derived aryl ethers and vanillin are essential platform chemicals that fulfil the demands for renewable aromatic compounds. Herein, an efficient heterogeneous catalyst is reported for reforming vanillin via a selective hydrodeoxygenation route to 2-methoxy-4-methyl phenol (MMP), a precursor to medicinal, food, and petrochemical industries. A series of MoCoO x @C catalysts were synthesized by decorating the Co-BTC MOF with different contents of MoO 3 rods, followed by carbonization. Among these catalysts, MoCoO x @C-2 afforded ∼99% vanillin conversion and ∼99% MMP selectivity at 150 °C in 1.5 h in an aqueous medium. In contrast, CoO x @C afforded ∼75% vanillin conversion and ∼85% MMP selectivity. Detailed catalyst characterization revealed that CoO x and Co 2 Mo 3 O 8 were the active species contributing to the higher activity of MoCoO x @C-2. The excellent H 2 -adsorption characteristics and acidity of MoCoO x @C-2 were beneficial to the hydrodeoxygenation of vanillin and other homologous compounds. The DFT adsorption energy calculations suggested the favourable interactions of vanillin and vanillyl alcohol with the Co 2 Mo 3 O 8 sites in MoCoO x @C-2. The catalyst could be efficiently recycled 5 times, with a negligible loss in activity after the 5th cycle. These findings provide a systematic explication of the active sites of the mixed metal oxide-based MoCoO x @C-2 catalyst for the selective hydrodeoxygenation of vanillin to MMP, which is important for the academic and industrial catalysis community.

Collisional cross-sections of inelastic rotational excitations of CN in its ground electronic state (X 2 Σ + ) by H + scattering are studied by the exact quantum mechanical close-coupling (CC) method at very low collision energies (0-600 cm -1 ) relevant to interstellar atmospheres. Ab initio rigid rotor potential energy surface computed at MRCI/ cc - p VTZ level of accuracy has been employed. Rate coefficients for the rotational excitations have also been calculated. The obtained results are compared with previous theoretical calculations and analyzed whether proton collisions could be significant sources for rotationally excited CN as a possible source for cosmic microwave background of about 3 K from the interstellar media., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Anusuri, Dhilip Kumar and Kumar.)

Highly porous, polyhedral metal-organic frameworks (MOFs) of Co(II)/Ni(II), {[M 6 (TATAB) 4 (DABCO) 3 (H 2 O) 3 ]·12DMF·9H 2 O} n (where M = Co(II) (1)/Ni(II) (2), H 3 TATAB = 4,4',4″- s-triazine-1,3,5-triyl-tri- p-aminobenzoic acid, and DABCO = 1,4-diazabicyclo[2.2.2]octane) have been synthesized solvothermally. Both MOFs 1 and 2 show a 2-fold interpenetrated 3D framework structure composed of dual-walled cages of dimension ∼ 30 Å functionalized with a high density of Lewis acidic Co(II)/Ni(II) metal sites and basic -NH- groups. Interestingly, MOF 1 shows selective adsorption of CO 2 with high heat of adsorption ( Q st ) value of 39.7 kJ/mol that is further supported by theoretical studies with computed binding energy (BE) of 41.17 kJ/mol. The presence of the high density of both Lewis acidic and basic sites make MOFs 1/2 ideal candidate materials to carry out co-catalyst-free cycloaddition of CO 2 to epoxides. Consequently, MOFs 1/2 act as excellent recyclable catalysts for cycloaddition of CO 2 to epoxides for high-yield synthesis of cyclic carbonates under co-catalyst-free mild conditions of 1 bar of CO 2 . Further, MOF 1 was recycled for five successive cycles without substantial loss in catalytic activity. Herein, rational design of rare examples of 3D polyhedral MOFs composed of Lewis acidic and basic sites exhibiting efficient co-catalyst-free conversion of CO 2 has been demonstrated.

A bifunctional, microporous Zn II metal-organic framework, [Zn 2 (NH 2 BDC) 2 (dpNDI)] n (MOF1) (where, NH 2 BDC=2-aminoterephthalic acid, dpNDI=N,N'-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF1 shows an interesting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99×3.58 Å and 4.58×5.38 Å decorated with pendent -NH 2 groups. Owing to the presence of a basic functionalized pore surface, MOF1 exhibits selective adsorption of CO 2 with high value of heat of adsorption (Q st =46.5 kJ mol -1 ) which is further supported by theoretically calculated binding energy of 48.4 kJ mol -1 . Interestingly, the value of Q st observed for MOF1 is about 10 kJ mol -1 higher than that of analogues MOF with the benzene-1,4-dicarboxylic acid (BDC) ligand, which establishes the critical role of the -NH 2 group for CO 2 capture. Moreover, MOF1 exhibits highly selective and sensitive sensing of the nitroaromatic compound (NAC), 2,4,6-trinitrophenol (TNP) over other competing NACs through a luminescence quenching mechanism. The observed selectivity for TNP over other nitrophenols has been correlated to stronger hydrogen bonding interaction of TNP with the basic -NH 2 group of MOF1, which is revealed from DFT calculations. To the best of our knowledge, MOF1 is the first example of an interpenetrated Zn II -MOF exhibiting selective adsorption of CO 2 as well as efficient aqueous-phase sensing of TNP; investigated through combined experimental and theoretical studies., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Proton and hydrogen atom time-of-flight spectra in collision energy range of E(trans) = 9.5-30 eV show that the endoergic charge transfer process in the H+ + CO system is almost an order of magnitude less probable than the elastic scattering [G. Niedner-Schatteburg and J. P. Toennies, Adv. Chem. Phys. LXXXII, 553 (1992)]. Ab initio computations at the multireference configuration interaction level have been performed to obtain the ground- and several low-lying excited electronic state potential energy curves in three different molecular orientations namely, H+ approaching the O-end and the C-end (collinear), and H+ approaching the CO molecule in perpendicular configuration with fixed CO internuclear distance. Nonadiabatic coupling terms between the ground electronic state (H+ + CO) and the three low-lying excited electronic states (H + CO+) have been computed and the corresponding diabatic potentials have been obtained. A time-dependent wavepacket dynamics study is modeled first involving only the ground and the first excited states and then involving the ground and the three lowest excited states at the collision energy of 9.5 eV. The overall charge transfer probability have been found to be approximately 20%-30% which is in qualitative agreement with the experimental findings.