Quadrupole and Octopole Moments of Heteroaromatic Rings

Abstract

Ab initio, second-order, Møller−Plesset perturbation theory calculations of quadrupole and octopole moments are reported for 36 different 6π-electron monocycles: benzene, 12 azines, pyrrole, 9 azoles, furan, 9 oxazoles, borazine, boroxine, and 1,2,4,3,5-trioxadiborole. Agreement with the limited experimental and computational data available is generally good.

Synthesis and Crystal Structure Differences between Fully and Partially Fluorinated β-Diketonate Metal (Co2+, Ni2+, and Cu2+) Complexes

“…The phenyl and pentafluorophenyl groups are clearly different orientation in 4. The phenyl group is flat with respect to the coordination plane (the dihedral angle between O1-C7-C8-C9-O2 and C1-C2-C3-C4-C5-C6 is 6.82 (16) • ), and the pentafluorophenyl group is highly twisted (that between O1-C7-C8-C9-O2 and C10-C11-C12-C13-C14-C15 is 56.76 (8) • ). On the other hand, the crystal structure of [Cu(DBM) 2 ] at 293 K is highly flat [31,32].…”

“…For example, a benzene molecule has a negative quadrupole moment, −29.0 × 10 −40 C m 2 [8] stabilizing a rectangular orientation of CH· · · π interaction [9] and a sliding orientation of π-π stacking. The negative charge of aromatic center also interacts the cationic source through cation· · · π interactions [10][11][12].…”

“…The negative charge of aromatic center also interacts the cationic source through cation· · · π interactions [10][11][12]. On the other hand, the electron charge of aromatic compounds can be controlled by fluorination (e.g., a hexafluorobenzene molecule which shows positive quadrupole moment, 31.7 × 10 −40 C m 2 ) [8] and unique electrostatic interactions, such as arene-perfluoroarene [13][14][15][16][17][18] and anion-π [19][20][21] interactions, which have attracted interests in a couple of decades. We have also synthesized several fluorinated compounds to control the electrostatic interactions and to design the metal· · · metal [22] and metal· · · π [23] arrangements through the interactions [24][25][26][27][28].…”

Azolylpentazoles as High‐Energy Materials: A Computational Study

“…Calculations showed that N 5 À and N 7 3À might be stabilized as transition-metal complexes such as Fe(N 5 ) 2 [49,50] or ScN 7 . [51,52] The aromaticity of pentazole [53±55] and its electric quadrupole moment [56] were also investigated. The combination of N 5 with a polynitrogen anion has also been studied by quantum chemical methods.…”

Structural and Molecular Orbital Properties of Some Boroxine Derivatives-A Theoretical Study

“…20 Apart from the synthetic approaches to the boroxine derivatives, there have been many theoretical studies on boroxine and its derivatives. Among them; Beckmann et al, investigated ring strain in boroxine rings, 21 Doerksen and Thakkar computed the bond orders, quadrupole and octopole moments of some heterocyclic molecules, including boroxine, 22,23 ring currents and aromaticity of monocyclic systems have been studied by Fowler and Steiner, 24 and Tossell investigated the structure, polarizability and vibrational spectra of boroxine. 25 It has been proposed that replacing hydrogen atoms of boron in borazine with more electronegative substituents, for example fluorines, will draw more electrons from nitrogen to boron, thereby enhancing the aromaticity of the molecule.…”