ABSTRACT
Both exohedral and endohedral complexes of second row elements doped X12Y12 (X = B, Al and Y = P) nano-cages are evaluated for thermodynamic stabilities, electronic properties and kinetic barriers. Interaction energies are calculated to deeply perceive the stability of these complexes. Further, interconversion of exohedral and endohedral complexes is explored through an unprecedented approach, where 2nd row elements translate into nano-cages through boundary crossing. Subsequently, the kinetic barriers for encapsulation and decapsulation are also investigated through PES scanning of all elements by passing through hexagon of nano-cages. Systematic investigations revealed that due to larger diameter, AlP nanocage exhibits low encapsulation barriers in comparison to BP nano-cage. Such as; the encapsulation barrier of F@AlP (7.57 kcal mol-1) is lower than that of F@BP (129.78 kcal mol-1). Moreover, distortion of nano-cages due to translation of elements is also estimated by distortion energies. Large distortion energies of 113.81/118.39 kcal mol-1 are noticed for exo-B@AlP/exo-C@BP complexes. In addition, the electronic properties for all the complexes are probed and depicted that the endohedral doping have remarkable influence on the electronic properties of the nanocage in comparison to exohedral doping. NBO charge analysis shows that Be metal delivers charges of 0.08 |e|/0.03 |e| to the AlP/BP nanocage, causing the later more electron rich. Contrary to Be, all other doped atoms show negative charges.
Subject(s)
Models, Molecular , ThermodynamicsABSTRACT
Alkaline earthide is a well-known class of the excess electron compounds with potential applications as NLO materials. In this study, all-cis-1,2,3,4,5,6-hexafluor-ocyclohexane C6H6F6 (1), a high polarized complexant having the largest dipole moment (6.2D) among all the known aliphatic hydrocarbons, is selected as a suitable molecule for designing a new series of excess electron molecules, alkaline-earthides. Geometric, thermodynamic and electronic properties of A-1-AE (A = Li, Na, K and AE = Be, Mg, Ca) are studied at M06-2X/6-31+G(d,p) level of theory. More specifically, alkaline-earthide nature is confirmed by distribution of densities in HOMOs, VIE values and NBO analysis. The alkaline earthide possess moderate complexation energies (-6.56 to -14.19 kcal/mol), which demonstrate their thermodynamic stability. These alkaline earthides possess very small excitation energies (0.54-1.64 eV) and very large first hyperpolarizabilities (up to 4.14 × 109 au). The higher hyperpolarizabilities values are attributed to the presence of excess electrons on alkaline earth metals which is confirmed through the partial density of states (PDOS) analysis. The hyperpolarizabilities are rationalized through two level model approach. Large hyperpolarizability values illustrate that the alkaline-earthides are a very promising entry into excess electron compounds.
Subject(s)
Electrons , Sodium , Ions , Potassium , Quantum TheoryABSTRACT
FEUDAL (f's essentially unaffected, d's accommodate ligands) is a longstanding bonding model in actinide chemistry, in which metal-ligand binding uses 6d-orbitals, with the 5f remaining non-bonding. The inverse-trans-influence (ITI) is a case where the model may break down, and it has been suggested that ionic and covalent effects work synergistically in the ITI. Here, we report an experimentally grounded computational study that quantitatively explores the ITI, and in particular the structure-directing role of f-orbital covalency. Strong donor ligands generate a cis-ligand-directing electrostatic potential (ESP) at the metal centre. When f-orbital participation, via overlap-driven covalency, becomes dominant via short actinide-element distances, this ionic ESP effect is overcome, favouring a trans-ligand-directed geometry. This study contradicts the accepted ITI paradigm in that here ionic and covalent effects work against each other, and suggests a clearly non-FEUDAL, structure-directing role for the f-orbitals.
