Superatoms-Induced Effects of Phenalenyl π-Dimer on NICS and NLO Properties: Not Always Enhancement

Abstract

The introduction of the Li3O and BeF3 can exhibit an interlayer charge-transfer transition character for pure phenalenyl (PLY) dimer. A considerable question emerged: Can we modulate the interlayer charge-transfer transition character with different superalkalis and superhalogens? In the present work, nine complexes were designed with three superalkalis (Li3O, Li3S, and Na3O) and three superhalogens (BeF3, BeCl3, and MgF3) introduced into the PLY dimers, respectively. Results showed that the geometric structure, interlayer charge transfer, and electron transition character of PLY dimer were alternated by the superalkalis and superhalogens, especially for superalkali, with the increasing atomic number for alkali metals, interlayer distance and interaction energy between PLY monomers increased, while first hyperpolarizability (βtot) decreased. The results of TD-DFT calculation indicated that the variation of βtot was mainly caused by the alteration of the difference of the dipole moments between the ground state and the crucial excited state Δμ. Otherwise, due to the introduction of superatoms, the distribution of HOMO and LUMO was changed greatly as compared to that of pure PLY dimer. In addition, aromaticity was also analyzed, and it was intriguing to find that introduction of superatoms caused asymmetric distribution of aromaticity along the central-carbon axis. All of the above consequences suggested that the introduction of superatoms was really an effective strategy to alter the structure and the nonlinear optical property of the system.

Recent Progress on the Design, Characterization, and Application of Superalkalis

“…Thereafter, further endeavors have been devoted to designing NLO molecules by doping superalkalis on different nanocages, including C 24 N 24 , Si 12 C 12 , C 20 , and B 40 . In addition, NLO materials can also be obtained by interacting superalkalis with other complexants, such as graphdiyne, hexamethylenetetramine, phenalenyl,– modified graphene, and P 4 molecules . Superalkalis can also be utilized as building blocks of alkalides,– which was first revealed by Wu and co‐workers .…”

Linear and second‐order nonlinear optical properties of B,N‐embedded double hetero[7]helicenes

“…In order to exhibit a strong second-order NLO response on a macroscopic scale, the molecule must have a larger first hyperpolarizability β value, so the design and synthesis of molecules with a larger first hyperpolarizability β value have become a popular research field. At present, molecular design strategies to improve the second-order NLO response mainly include introducing electron donor(D)/acceptor(A) groups with different intensities [20][21][22][23], increasing strength of the conjugated chain [24][25][26], changing the functional groups of the studied system [27] and incorporating transitions metals into compounds, etc [28][29][30][31].…”