Theoretical prediction of donor-acceptor type novel complexes with strong noble gas-boron covalent bond.

The experimental identification of NgBeO molecules, followed by the recent theoretical exploration of super-strong NgBO+ (Ng = He-Rn) ions motivated us to investigate the stability of iso-electronic NgBNH+ (Ng = He-Rn) ions using various ab initio-based quantum chemical methods. The hydrogen-like chemical behavior of gold in small clusters and molecules also inspired us to study the nature of the bonding interactions in NgBNAu+ ions compared to that in NgBNH+ ions. The calculated Ng-B bond lengths in the predicted ions have been found to be much lower than the corresponding covalent limits, indicating a covalent Ng-B interaction in both the NgBNH+ and NgBNAu+ ions. In addition, the Ng-B bond dissociation energies are found to be in the range of 136.7-422.8 kJ mol-1 for NgBNH+ and 77.4-319.1 kJ mol-1 for NgBNAu+, implying the stable nature of the predicted ions. Interestingly, the Ng-B bond length (except for Ne) is the lowest reported to date together with the highest He-B and Ne-B binding energies considering all the neutral and cationic complexes containing Ng-B bonding motifs. Moreover, the natural bonding orbital (NBO) and electron density-based atoms-in-molecule (AIM) analysis reveal the covalent nature of the Ng-B bond in the predicted ions. Furthermore, the energy decomposition analysis together with the natural bond orbital in the chemical valence (EDA-NOCV) studies indicate that the orbital interaction energy is the main contributor to the total attraction energy in the Ng-B bonds. All the calculated results indicate the hydrogen-like chemical behavior of gold in the predicted NgBNM+ ions, showing further evidence of the concept of "gold-hydrogen analogy". Also, for comparison, the corresponding Cu and Ag analogs are investigated. All the computed results together with the experimental identification of the NgMX (Ng = Ar-Xe; M = Cu, Ag, Au; X = F, Cl), ArOH+, and NgBeO (Ng = Ar-Xe) systems clearly indicate that it may be possible to prepare and characterize the predicted NgBNM+ ions experimentally using suitable technique(s).

Understanding the excited state dynamics and redox behavior of highly luminescent and electrochemically active Eu(III)-DES complex.

Deep eutectic solvents (DES) are considered a novel class of environmentally benign molecular solvents that are considered as potential solvents for nuclear fuel reprocessing, material recycling, and many other technological applications in both research and industry. However, there is a complete dearth of understanding pertaining to the behavior of metal ions in DES. Herein, we have investigated the speciation, complexation behavior, photochemistry, and redox properties and tried to obtain insight into the chemical aspects of the europium ion in DES (synthesized from heptyltriphenylphosphonium bromide and decanoic acid). The same has been probed using time-resolved photoluminescence (TRPL), cyclic voltammetry (CV), synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations. TRPL indicated the stabilization of europium in the +3 oxidation state, favoring the potential of the Eu(III)-DES complex to emit red light under near UV excitation and the existence of inefficient energy transfer between DES and Eu3+. EXAFS analysis revealed the presence of Eu-O and Eu-Br, which represent the local surroundings of Eu3+ in the Eu(III)-DES complex. TRPL measurement has also suggested two distinct local environments of europium ions in the complex. DFT calculations supported the EXAFS findings, confirming that the Eu(III)-DES structure involves not only the oxygen atom of decanoic acid but also the oxygen atoms from the nitrate ions, contributing to the local coordination of Eu(III). Electrochemical studies demonstrated that the redox reaction of Eu(III)/Eu(II) in DES displays quasi-reversible behavior. The reaction rate was observed to increase with higher temperatures. The findings of this study can contribute to the understanding of the fundamental properties and potential applications of this luminescent and electrochemically active complex and pave the way for further studies and the development of novel materials with enhanced luminescent and electrochemical properties.

Experimental and Theoretical Investigation on the Extractive Mass Transfer of Eu3+ Ions Using Novel Amide Ligands in 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide.

Novel amide ligands in the ionic liquid (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) were utilized for the liquid-liquid biphasic mass transfer of Eu3+ ions from aqueous acidic waste solution. The cation exchange mechanism was found to be operative with the formation of [Eu(NO3)2L3]+ species (L = 4-chloro-N-(1-methyl-1H-pyrazol-3-yl)picolinamide). However, the presence of an inner-sphere water molecule was revealed by density functional theory (DFT) calculations. The viscosity-induced slower kinetics was evidenced during mass transfer, which was improved by increasing temperature. The process was exothermic in nature. The improvement in the kinetics of extractive mass transfer at higher temperatures is evinced by a reduction in the distribution ratio value. The spontaneity of the reaction was evidenced through the negative Gibbs free energy value, whereas the process enhances the entropy of the system, probably by releasing water molecules at least partially during complexation. The structures of bare ligands and complexes have been optimized by using DFT calculations. A high value of complexation energy, solvation energy, and associated enthalpy and free energy change reveal the efficacy in binding Eu with O and N donor atoms. In addition, natural population analysis, atoms-in-molecules analysis, and energy decomposition analysis have been employed to explore the nature of bonding existing in Eu-O and Eu-N bonds.

Unusual Spin States in Noble Gas Inserted Noble Metal Halocarbenes, FNgCM (Ng = Kr, Xe, Rn; M = Cu, Ag, Au).

Recent experimental detection of noble gas (Ng) inserted fluorocarbenes, viz., FKrCF and FXeCF, which were theoretically predicted by our group earlier and very recent experimental evidences on gold-halogen analogy motivated us to explore the possibility of the existence of noble gas inserted noble metal fluorocarbene, FNgCM (Ng = Kr, Xe, and Rn; M = Cu, Ag, and Au) molecules. Ab initio quantum chemical calculations have been performed to investigate structure, stability, vibrational frequency, charge distribution and bonding analysis of FNgCM molecules by employing DFT, MP2, and CCSD(T) methods. For the purpose of comparison FNgCH molecules have also been studied. One of the important outcomes of the study is that the predicted FNgCH, FNgCCu and FNgCAg molecules are more stable in their triplet electronic states, whereas the FNgCAu molecules are found to be more stable in their singlet potential energy surface, similar to the recently observed FNgCF (Ng = Kr and Xe) molecules, although the singlet state is the lowest energy state for all the precursor carbene molecules. The gold atom behaves as a better electron donor due to the pronounced relativistic effect as compared to hydrogen, copper and silver atoms, resulting in stabilization of the singlet carbene molecule indicating halogen like chemical behavior of gold. These molecules are found to be thermodynamically stable with respect to all plausible 2-body and 3-body dissociation channels, except the one that leads to the formation of the global minimum products. However, metastable nature of the predicted molecules has been proved by studying the saddle point corresponding to the transition from the minima to the global minimum products. Sufficient barrier heights provide the kinetic stability to the predicted FNgCM molecules, which prevent them from dissociating into their respective global minimum products. All the results clearly indicate that the F-Ng bond is mostly ionic in nature with certain amount of covalent character while Ng-C bond is found to be covalent in nature. Furthermore, atoms-in-molecule (AIM), energy decomposition analysis (EDA) and charge distribution analyses suggest that the predicted FNgCM molecules essentially exist in the form of [F]δ-[NgCM]δ+. The calculated results also indicate that it may be possible to prepare and characterize the predicted molecules by suitable experimental technique(s).

Design and Synthesis of BODIPY-Hetero[5]helicenes as Heavy-Atom-Free Triplet Photosensitizers for Photodynamic Therapy of Cancer.

Designing heavy-atom-free triplet photosensitizers (PSs) is a challenge for the efficient photodynamic therapy (PDT) of cancer. Helicenes are twisted polycyclic aromatic hydrocarbons (PAHs) with an efficient intersystem crossing (ISC) that is proportional to their twisting angle. But their difficult syntheses and weak absorption profile in the visible spectral region restrict their use as heavy-atom-free triplet PSs for PDT. On the other hand, boron-containing PAHs, BODIPYs are highly recognized for their outstanding optical properties. However, planar BODIPY dyes has low ISC and thus they are not very effective as PDT agents. We have designed and synthesized fused compounds containing both BODIPY and hetero[5]helicene structures to develop red-shifted chromophores with efficient ISC. One of the pyrrole units of the BODIPY core was also replaced by a thiazole unit to further enhance the triplet conversion. All the fused compounds have helical structure, and their twisting angles are also increased by substitutions at the boron centre. The helical structures of the BODIPY-hetero[5]helicenes were confirmed by X-ray crystallography and DFT structure optimization. The designed BODIPY-hetero[5]helicenes showed superior optical properties and high ISC with respect to [5]helicene. Interestingly their ISC efficiencies increase proportionally with their twisting angles. This is the first report on the relationship between the twisting angle and the ISC efficiency in twisted BODIPY-based compounds. Theoretical calculations showed that energy gap of the S1 and T1 states decreases in BODIPY-hetero[5]helicene as compared to planar BODIPY. This enhances the ISC rate in BODIPY-hetero[5]helicene, which is responsible for their high generation of singlet oxygen. Finally, their potential applications as PDT agents were investigated, and one BODIPY-hetero[5]helicene showed efficient cancer cell killing upon photo-exposure. This new design strategy will be very useful for the future development of heavy-atom-free PDT agents.

Prediction of donor-acceptor-type novel noble gas complexes in the triplet electronic state.

Closed-shell noble gas (Ng) compounds in the singlet electronic state have been extensively studied in the past two decades after the revolutionary discovery of 1HArF molecule. Motivated by the experimental identification of very strong donor-acceptor-type singlet-state Ng complex 1ArOH+, in the present article, for the first time, we report new donor-acceptor-type noble gas complexes in the triplet electronic state (3NgBeN+ (Ng = He-Rn)), where most of the Ng-Be bond lengths are smaller than the corresponding covalent limits. The newly proposed complexes are predicted to be stable by various computational tools, including coupled-cluster and multireference-based methods, with strong Ng-Be bonding (40.4-196.2 kJ mol-1). We have also investigated 3NgBeP+ (Ng = He-Rn) complexes for the purpose of comparison. Various computational results, including the structural parameters, bonding energies, vibrational frequencies, and atoms-in-molecule properties suggest that it may be possible to prepare and characterize these triplet state complexes through suitable experimental technique(s).

Superstrong Chemical Bonding of Noble Gases with Oxidoboron (BO+) and Sulfidoboron (BS+).

Inspired by the overwhelming exploration of noble gas-boron (Ng-B) bond containing chemical compounds, the stability of the Ng bound BY+ and AlY+ (Y = O and S) has been investigated by using various ab initio based quantum chemical methods. Ng atoms are found to form exceptionally strong bonds with BO+ species in the predicted NgBO+ (Ng = He-Rn) complexes with remarkably high Ng-B dissociation energies ranging from 138.0 to 462.2 kJ mol-1 for the He-Rn series. It is the highest ever Ng-B binding energy in conjunction with the smallest Ng-B bond length for any of the cationic species involving a Ng-B bond as reported until today. More importantly, the calculated Ng-B bond lengths have been found to be much lower than the respective covalent limits in both NgBO+ and NgBS+ ions. The electronegativity difference between O and S atoms has been reflected nicely in the Ng-B and Ng-Al binding energies, which are found to be 91.9-346.5, 9.6-169.2, and 6.8-142.1 kJ mol-1 in NgBS+, NgAlO+, and NgAlS+, respectively. The strong covalent bonding between Ng and B/Al atoms in the predicted chemical systems has also been supported by the natural bonding orbital (NBO) and electron density based atoms-in-molecule (AIM) analysis. In addition, the energy decomposition analysis (EDA) in combination with the natural bond orbital for chemical valence (NOCV) indicates that the orbital interaction term is the prime contributor to the total attraction energy in the Ng-B and Ng-Al bonds. Furthermore, Ng-B and Ng-Al bonding can be assessed using the donor-acceptor model where the σ-electron donation that takes place from Ng (HOMO) → XY+ (LUMO) (X = B and Al; Y = O and S) is the major contributor to the orbital interaction energy. All the computational results along with the very recent experimental observation of ArOH+ and NgMX (Ng = Ar-Xe; M = Cu, Ag, Au; X = F, Cl) clearly indicate that it might be possible to synthesize and characterize these superstrong complexes, NgXY+ (Ng = He-Rn; X = B and Al; Y = O and S), under suitable experimental technique(s).

Existence of noble gas-inserted phosphorus fluorides: FNgPF2 and FNgPF4 with Ng-P covalent bond (Ng = Ar, Kr, Xe and Rn).

The scarce literature on noble gas (Ng)-phosphorous chemical bonding and our recent theoretical prediction of the FNgP molecule motivate us to explore a unique novel class of neutral noble gas-inserted phosphorus trifluoride and pentafluoride molecules, i.e., FNgPF2 and FNgPF4 (Ng = Ar, Kr, Xe, and Rn). The predicted molecules have been designed by inserting an Ng atom between the F and P atoms in the PF3 and PF5 molecules. The minima and saddle point geometries of all the FNgPFn (n = 2 and 4) molecules have been optimized using density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2). The coupled cluster theory (CCSD(T)) method is also used to optimize the FNgPF2 molecules to test the performance of the above-mentioned methods. The predicted FNgPF2 and FNgPF4 molecules are found to be energetically stable with respect to all the probable 2-body and 3-body dissociation channels, except for the one leading to the global minimum products (Ng + PF3 and Ng + PF5). The existence of large barrier heights corresponding to the saddle point geometries is responsible for the kinetic stability of the metastable FNgPFn (n = 2 and 4) molecules, which prevents them from dissociating into their global minima products. The optimized structural parameters, energetics and harmonic vibrational frequency analysis suggest that the Ng-P bond is covalent in nature, while the F-Ng bond is mostly ionic in nature with some degree of covalency in the predicted molecules. In fact, the Ng-P bond length in the experimentally observed Ng-PF3 van der Waals complex is reduced significantly in the isomeric FNgPF2 molecule, almost leading to a conventional covalent Ng-P bond (cf. 4.152 vs. 2.413 Å for the Kr-P bond). Furthermore, the charge distribution and the AIM analysis also confirm the above-mentioned conclusion and indicate that the predicted FNgPF2 and FNgPF4 molecules can be represented as [F]δ-[NgPF2]δ+ and [F]δ-[NgPF4]δ+, respectively. All the computational results strongly reinforce the possible existence of these predicted FNgPFn (n = 2 and 4) molecules and clearly indicate that it may be possible to synthesize and characterize these molecules under suitable experimental technique(s).

Gold-Hydrogen Analogy in Small-Sized Hydrogen-Doped Gold Clusters Revisited.

The analogy between gold and hydrogen is a subject of long-standing debate. In the present work, we examine the validity of the gold-hydrogen analogy in a series of small-sized H-doped gold clusters, Aun-1 H with n varying between 2 and 10 and also investigate its dependence on the cluster size. Keeping in mind the importance of the role of structures, we make use of the genetic algorithm coupled with a density functional theory based method to exhaustively search and identify the energetically low-lying structures of each of the H-doped gold clusters. These lower energy structures of H-doped and pristine gold clusters are then employed to carry out the calculations of their electronic properties, stability analysis as well as their reactivity towards the adsorption and activation of CO and O2 molecules. Our study shows that in line with the gold-hydrogen analogy, both electronic properties and the adsorption/activation characteristics of H-doped gold clusters remain very similar to those of pristine gold clusters.

The Decisive Role of Spin States and Spin Coupling in Dictating Selective O2 Adsorption in Chromium(II) Metal-Organic Frameworks.

Invited for the cover of this issue are Sourav Pal, Gopalan Rajaraman and co-workers at the Indian Institute of Technology Bombay, the Bhabha Atomic Research Centre and the Indian Institute of Science Education and Research. The image depicts how a mixture of atmospheric gases such as CO2 , H2 , N2 and O2 can be selectively separated using a Cr metal-organic framework where spin state and spin coupling play a crucial role. Read the full text of the article at 10.1002/chem.202104526.

Stability-Order Reversal in FSiY and FYSi (Y = N and P) Molecules after the Insertion of a Noble Gas Atom.

Recent theoretical prediction and experimental identification of fluorinated noble gas cyanides and isocyanides motivate us to explore a unique novel series of neutral noble gas-inserted heavier cyanofluoride isomers, FNgYSi and FNgSiY (Ng = Kr, Xe, and Rn; Y = N and P), theoretically using quantum chemical calculations. The concerned minima and saddle point geometries have been optimized using DFT, MP2, and CCSD(T) methods. The precursor molecule FSiY is more stable than its isomer FYSi, and the stability order is found to be reversed after the insertion of a noble gas (Ng) atom into them which is in contrast to the previously reported FCN/FNC systems where the stability order in the precursors remains intact after the insertion of a Ng atom into them. The predicted FNgYSi molecules are metastable in nature as they are kinetically stable but thermodynamically unstable with respect to the global minima products (FYSi and Ng). All the calculations for the corresponding FNgSiY molecules clearly indicate that the less stable FNgSiY behaves similarly to the FNgYSi in all respects. The energetics, force constant, and spectroscopic data strongly reinforce the possibility of occurrence of these predicted FNgYSi and FNgSiY molecules which might be experimentally realized under suitable cryogenic condition(s).

The Decisive Role of Spin States and Spin Coupling in Dictating Selective O2 Adsorption in Chromium(II) Metal-Organic Frameworks.

The coordinatively unsaturated chromium(II)-based Cr3 [(Cr4 Cl)3 (BTT)8 ]2 (Cr-BTT; BTT3- =1,3,5-benzenetristetrazolate) metal-organic framework (MOF) has been shown to exhibit exceptional selectivity towards adsorption of O2 over N2 /H2 . Using periodic density functional theory (DFT) calculations, we attempted to decipher the origin of this puzzling selectivity. By computing and analyzing the magnetic exchange coupling, binding energies, the partial density of states (pDOS), and adsorption isotherms for the pristine and gas-bound MOFs [(Cr4 (X)4 Cl)3 (BTT)8 ]3- (X=O2 , N2 , and H2 ), we unequivocally established the role of spin states and spin coupling in controlling the gas selectivity. The computed geometries and gas adsorption isotherms are consistent with the earlier experiments. The binding of O2 to the MOF follows an electron-transfer mechanism resulting in a CrIII superoxo species (O2 .- ) with a very strong antiferromagnetic coupling between the two centers, whereas N2 /H2 are found to weakly interact with the metal center and hence only slightly perturb the associated coupling constants. Although the gas-bound and unbound MOFs have an S=0 ground state (GS), the nature of spin the configurations and the associated magnetic exchanges are dramatically different. The binding energy and the number of oxygen molecules that can favorably bind to the Cr center were found to vary with respect to the spin state, with a significant energy margin (47.6 kJ mol-1 ). This study offers a hitherto unknown strategy of using spin state/spin couplings to control gas adsorption selectivity in MOFs.

Role of metcar on the adsorption and activation of carbon dioxide: a DFT study.

Metallocarbohedrenes or metcars belong to one of the classes of stable nanoclusters having a specific stoichiometry. In spite of the available theoretical and experimental studies, the structure of pristine Ti8C12 metcar is still uncertain. We study the geometric structure of a titanium metcar, Ti8C12, together with its electronic properties and chemical activity towards adsorption and activation of CO2 molecule by means of density functional theory. Our results suggest that the CO2 molecule is strongly adsorbed and undergoes a significantly high degree of activation onto the Ti8C12 metcar. The migration of charge from titanium metcar to CO2 molecule attributes the high degree of activation of this molecule. In the infrared vibrational spectra for CO2 molecule adsorbed onto Ti8C12, we find a new signal which is absent in the corresponding spectra for gaseous CO2. In addition to adsorption energy, we also estimate the energy barrier for the dissociation of CO2 molecule to CO and O fragments on a Ti8C12 cluster. As a whole, this work reveals the ground state geometry of Ti8C12 metcar and highlights the role of this metcar in CO2 adsorption and activation, which are the key steps in designing potential catalysts for CO2 capture and its conversion to industrially valuable chemicals.

Adsorption and Activation of CO2 on Small-Sized Cu-Zr Bimetallic Clusters.

Adsorption and activation of CO2 is a key step in any chemical reaction, which aims to convert it to other useful chemicals. Therefore, it is important to understand the factors that drive the activation process and also search for materials that promote the process. We employ the density functional theory to explore the possibility of using small-sized bimetallic Cu-Zr clusters, Cu4-nZrn, with n = 1-3 for the above-mentioned key step. Our results suggest that after adsorption, a CO2 molecule preferably resides on Zr atoms or at the bridge and triangular faces formed by Zr atoms in bimetallic Cu-Zr clusters accompanied with its high degree of activation. Importantly, maximum activation occurs when CO2 is adsorbed on the CuZr3 cluster. Interestingly, we find that the adsorption energy of CO2 can be tuned by varying the extent of the Zr atom in Cu-Zr clusters. We rationalize the high adsorption of CO2 with the increase in the number of Zr atoms using the d-band center model and the concept of chemical hardness. The strong chemisorption and high activation of CO2 are ascribed to charge migration between Cu-Zr clusters and the CO2 molecule. We find an additional band in the infrared vibrational spectra of CO2 chemisorbed on all of the clusters, which is absent in the case of free CO2. We also observe that the energy barriers for the direct dissociation of the CO2 molecule to CO and O decrease significantly on bimetallic Cu-Zr clusters as compared to that on pure Cu4. In particular, the barrier heights are considerably small for Cu3Zr and CuZr3 clusters. This study demonstrates that Cu3Zr and CuZr3 clusters may serve as good candidates for activation and dissociation of the CO2 molecule.

Adsorption and activation of CO2 on Zrn (n = 2-7) clusters.

The first step in the conversion of CO2 to useful chemicals involves the adsorption of this molecule on a catalyst accompanied with its high degree of activation. In this paper, we explore the efficacy of small sized zirconium clusters, Zrn (n = 2-7), in the adsorption and activation of the CO2 molecule by using the density functional theory based ab initio method. The results of our calculations provide compelling evidence for the chemisorption and very high degree of activation of CO2 with the elongation of the C-O bond in the range of 1.27-1.42 Å compared to 1.16 Å for free CO2 and the deformation of the O-C-O bond angle from linear to 115-136°. This activation takes place through a charge migration from the Zrn cluster to the CO2 molecule resulting in the formation of CO2δ- species. To assess the catalytic potential of Zr-clusters for CO2 conversion, we also analyse the reaction pathways and the transition barrier heights for the dissociation of CO2 (CO2 → CO + O) on all the Zrn clusters. Our results for the dissociation of CO2 to CO and O fragments reveal that the transition barrier is small for all the Zrn clusters except for Zr2 and Zr4 and it attains a minimum value of 0.11 eV for an isomer of the Zr6 cluster. The present work clearly demonstrates that small-sized monometallic Zr-clusters are highly efficient in activating and dissociating a CO2 molecule adsorbed on these clusters.

Anomaly in the stability of the hydroxides of icosagens (B and Al) and their noble gas (Xe and Rn) derivatives: a comparative study.

Motivated by the discovery of neutral noble gas hydrides, herein, we have explored the possibility of the existence of a novel class of neutral noble gas compounds, HNgBO, HNgOB, HNgAlO and HNgOAl (Ng = Xe and Rn), through the insertion of a Ng atom into the hydroxides of icosagens and their isomers, namely, HBO, HOB, HAlO and HOAl. Second-order Møller-Plesset perturbation theory (MP2), density functional theory (DFT), and coupled-cluster theory (CCSD(T))-based methods have been employed to investigate the structures, stabilities, energetics, harmonic vibrational frequencies, and charge distribution of the predicted molecules. The HXeBO, HXeOAl, HRnBO, HRnAlO and HRnOAl molecules are found to be thermodynamically stable with respect to all plausible 2-body and 3-body dissociation channels except the 2-body dissociation pathway, leading to the formation of global minimum products (Ng + HBO), (Ng + HOAl) and (Ng + HAlO). However, the very large activation energy barrier heights provide enough kinetic stability to the predicted metastable molecules, which in turn can prevent them from dissociating into the global minimum products. Between the HNgBO-HNgOB isomers, HNgBO is found to be more stable, where both HNgBO and the precursor molecule HBO are linear. On the other hand, HNgOAl is more stable between the HNgAlO-HNgOAl isomers, where the precursor molecule HOAl is bent and HNgOAl is linear in contradiction and in agreement with Walsh's rule, respectively. Moreover, in contrast to the more stable HNgBO case, where the Ng atom is bonded with the icosagen atom, in the more stable HNgOAl, the Ng atom is connected to the chalcogen atom. All the detailed aforementioned analyses concerning the predicted molecules clearly indicate that a strong covalent bond exists between the H and Ng atoms, while an ionic interaction is found between the Ng and B atoms in HNgBO and Ng and O atoms in the HNgOAl molecules. In addition, the charge distribution and atoms-in-molecules (AIM) analyses are in agreement with the above-mentioned conclusion and also suggest that the predicted metastable HNgBO and HNgOAl molecules should essentially exist in the form of [HNg]+[BO]- and [HNg]+[OAl]-, respectively. All the calculated results reported in this work indicate that it might be possible to prepare and characterize the predicted molecules via suitable experimental technique(s) under cryogenic conditions.

Unprecedented stability enhancement of multiply charged anions through decoration with negative electron affinity noble gases.

The present communication reports unprecedented stabilization of multiply charged anion, B12F122-, through insertion of noble gas (Ng) atoms possessing negative electron affinity into B-F bonds, resulting in the formation of stable icosahedral B12Ng12F122-, where the HOMO is stabilized significantly and the binding energy of the second excess electron is increased remarkably. Unprecedented stability enhancement with Ng is attributed to a strong covalent B-Ng bond, increased charge delocalization and increased electrostatic interaction between the oppositely charged centers.

Quantum chemical prediction of a superelectrophilic dianion and its binding with noble gas atoms.

The present communication shows an unprecedented superelectrophilic behaviour of dianion [BeB11(CN)11]2-, containing a positively charged electrophilic center embedded in a negatively charged framework. This dianion is shown to form stable [NgBeB11(CN)11]2- (Ng = He, Ne, Ar, Kr and Xe) compounds associated with either a Ng-Be or Ng-B bond. The dianion [BeB11(CN)11]2- binds covalently with Ar, Kr and Xe via its uncoordinated B atom.

Lanthanide and actinide doped B12H122- and Al12H122- clusters: new magnetic superatoms with f-block elements.

In recent years, actinide containing clusters have attracted immense attention because of the distinctive bonding properties of their 5f and 6d electrons. In this context, in the present work, we have studied the isoelectronic series of actinide (An = Np+, Pu2+, Am3+) doped B12H122- and Al12H122- clusters using density functional theory (DFT). Similarly, corresponding isoelectronic lanthanide (Ln = Pm+, Sm2+, Eu3+) doped clusters are also investigated using DFT for comparison. Both exohedral and endohedral metal doped Al12H122- clusters are investigated in various possible spin states, whereas for B12H122- only exohedral metal doped clusters are studied due to its smaller cage diameter. Among all the metal doped clusters, the exohedral metal doped B12H122- and Al12H122- clusters in a septet spin state with retained high spin population on the doped actinide ion, are the most stable, indicating that all these doped clusters are magnetic in nature. The high stability of exohedral clusters is due to small steric repulsion as compared to that in the corresponding endohedral clusters. A prominent charge transfer from cage to metal ion is responsible for the strong interaction of the doped metal ion with the cage atoms. The studied Ln@B12H122- (Ln@Al12H122-) and An@B12H122- (An@Al12H122-) clusters are not only thermodynamically stable, but also kinetically stable. Metal ion encapsulated endohedral Al12H122- clusters are found to satisfy the 32-electron principle corresponding to the completely filled s, p, d and f shells of the central f-block atom. Theoretical predictions of these lanthanide and actinide doped stable B12H122- and Al12H122- clusters could encourage experimentalists for the preparation of these metal-doped clusters. Thus, the present work offers borane and alane clusters as new hosts for encapsulating radioactive actinides. Furthermore, various functional derivatives of these actinide doped B12H122- clusters may find applications in the field of radiation medicine.

Predicted M(H2)12n+ (M = Ac, Th, Pa, U, La and n = 3, 4) complexes with twenty-four hydrogen atoms bound to the metal ion.

Herein, we have shown that La(iii), Ac(iii), Th(iii), Th(iv), Pa(iv) and U(iv) can directly bind with a maximum of 24 hydrogen atoms in M(H2)12 in the first sphere of coordination, which would be a new record in any metal-hydrogen complex investigated at the molecular level, where all the hydrogen atoms are directly connected to the central metal ion through M-η2(H2) bonds. Moreover, Ac(H2)n3+ (n = 9-12) systems satisfy the 18-electron rule.