RESUMEN
Neutral four-membered rings with 4nâ electrons are generally Hückel antiaromatic. On the other hand, 4n electron system can also be Möbius aromatic, although identification has escaped so far. A recent study of double Möbius aromaticity has been put forwarded in the D2h symmetric singlet ground state of four member Pa2B2 ring. Although interesting, but the synthesis possesses a significant challenge as Pa is rare, highly radioactive and toxic. Herein, a synthetically viable four membered Rh2B2 cluster is proposed which contains double Möbius aromaticity. Interestingly, the three membered RhB2 - cluster also possess Möbius aromaticity and is the smallest ring to show such phenomenon.
RESUMEN
Planar hypercoordination has sparkled interest among the researchers from last few decades. Most of the elements in the Periodic Table have shown this remarkable structural feature. However, the smallest element, hydrogen, is missing in the list. No evidence is there in the literature. Herein, we introduce the first planar pentacoordinate hydrogen atom (ppH) in the global minimum geometry of Li5 H6 - cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicentre bonding with five surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride which is strongly attracted by the positively charged surrounding lithium centres. The ppH structure is stabilized by strong electrostatic attraction as well as extensive multicentre bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in gas phase.
RESUMEN
Planar hypercoordinate structures are emerging tremendously. Most of the second-row elements from the periodic table exhibit this remarkable structural feature. Planar tetracoordinate fluorine (ptF) atoms were also predicted in group 13 supported clusters. However, high-level ab initio calculations nullified the fact and established that all these ptFs were not minimum energy structures on the potential energy surface. Thus, a true ptF is still scarce in the literature. Herein, we propose the unprecedented ptF as the global minimum of the C2V symmetric H3Li4F- cluster. Heavier alkali metals (Na and K) showed similar results. Both density functional theory (DFT) and ab initio calculations revealed that the ptF structure is a real minimum and indeed, the global minimum. Bonding analysis indicates that the central fluorine atom is stabilized by multicentre bonding with four surrounding Li atoms. Natural charge analysis reveals that the fluorine atom is negatively charged, which is strongly attracted by the positively charged surrounding lithium centres, thereby imparting significant electrostatic attraction. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in the gas phase.
RESUMEN
Despite the long list of planar tetracoordinate atoms, hydrogen is elusive. This is especially due to the inherent ability of hydrogen to form multicenter bonds with other centers. Herein, we introduce the first planar tetracoordinate hydrogen atom (ptH) in the global minimum geometry of a C2v symmetric Li4H4- cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicenter bonding with four surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride, which is strongly attracted by the positively charged surrounding lithium centers. The ptH structure is stabilized by strong electrostatic attraction as well as extensive multicenter bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in the gas phase. Introduction of a heavier alkali metal such as sodium makes the planar C2v cluster a local minimum with slightly higher energy than the linear global minimum geometry.
RESUMEN
Due to the increasing concentration of CO2 in the atmosphere and its negative effect on the environment, selective adsorption of CO2 from flue gas has become significantly important. In this study, we have considered a Zn-doped lithium cluster, ZnLi5+ cluster, featuring a planar pentacoordinate Zn centre, as a potential candidate for selective CO2 capture and separation from a flue gas mixture (CH4, CO2, N2). The binding energy calculation and non-covalent interaction study showed that CO2 molecules bind relatively strongly as compared to N2 and CH4 molecules. The metal cluster can bind five CO2, five CH4, and four N2 molecules with average binding energies of -9.2, -4.4, and -6.1 kcal mol-1, respectively. Decomposition of the binding energy through symmetry-adapted perturbation theory analysis reveals that the electrostatic component plays a major role. The cationic cluster may be a promising candidate for selective CO2 capture and can be used as a pollution-controlling agent. The calculated adsorption energy of H2S is quite closer to that of CO2, suggesting competitive adsorption between CO2 and H2S. The adsorption energies of H2O and NH3 are higher compared to CO2, indicating that these gases may be a potential threat to CO2 capture.
RESUMEN
Quantum chemical calculations have been carried out to investigate the hydrogen adsorption characteristics of the Li4B2 cluster. Calculations reveal that the cluster can adsorb a maximum of thirteen H2 molecules reaching a considerably high gravimetric density of 34.66 wt%. The nature of the interaction between the H2 molecule and Li center has been investigated within the realm of quantum theory of atoms in molecules which revealed the non-covalent character. The fate of H2 absorption by the cluster has been studied in the course of a 2000 fs time evolution through Born-Oppenheimer molecular dynamics simulations at different temperatures. The outcomes reveal that the H2 molecules are strongly bound at 77 K and get slowly released at elevated temperatures.
RESUMEN
Quantum chemical calculations have been carried out to investigate the hydrogen storage capacity of Be2 (NLi)2 cluster. Calculations reveal that the cluster can take up to eight H2 molecules reaching a maximum gravimetric density of 21.04 wt%. Six H2 molecules bind at the Li atoms and two H2 bind at the Be atoms with moderate binding energy which is required for reversible storage of H2 . Symmetry-adapted perturbation analysis reveals the significant contribution of electrostatic and induction and very minor contribution of dispersion toward the total interaction energy. Molecular dynamics simulations reveal that the H2 molecules are strongly bound at 77 K and get slowly released at elevated temperatures.
RESUMEN
The Lewis basic character of alkali metals forming donor-acceptor complexes is a very rare phenomenon. No Lewis adduct with an alkalide as the Lewis basic centre has ever been reported. Herein, we theoretically designed EXH2- (E = Li, Na, K; X = Be, Mg, Ca) clusters which represent the first true example of Lewis adducts with alkalides as the two-electron donor basic sites. Our high level ab initio calculations reveal the formation of an unprecedented E:- â XH2 donor-acceptor interaction. Topological analysis within the realm of the electron localization function confirms this bonding scenario. The bonding scenario is exactly replicated in all the clusters, rendering support to our proposal. The calculated bond dissociation energies are significant, suggesting their possible spectroscopic identification.
RESUMEN
Planar hypercoordinate structures are gaining immense attention due to the shift from common paradigm. Herein, our high level ab initio calculations predict that planar pentacoordinate aluminium and gallium centres in Cu5Al2+ and Cu5Ga2+ clusters are global minima in their singlet ground states. These clusters are thermodynamically and kinetically very stable. Detailed electronic structure analyses reveal the presence of σ-aromaticity which is the driving force for the stability of the planar form.
RESUMEN
Planar pentacoordinate zinc group elements, (M = Zn, Cd, Hg) were computationally found to be at a global minimum in Li5M+ clusters. The stability of these clusters is due to the presence of multicentric bonds. The central element (Zn, Cd, Hg) in each cluster features a negative oxidation state owing to the in-plane electron donation by the Li5+ framework. A similar global minimum planar pentacoordinate structure is found in Na5Zn+ and Na5Cd+ clusters.
