Rational Design, Stabilities and Nonlinear Optical Properties of Non-Conventional Transition Metalides; New Entry into Nonlinear Optical Materials

Optimization of nonlinear properties of C6O6Li6-doped alkalides via group I/III doping for unprecedented charge transfer and advancements in optoelectronics

The design and synthesis of nonlinear optical (NLO) materials are rapidly growing fields in optoelectronics. Considering the high demand for newly designed materials with superior optoelectronic characteristics, we investigated the doping process of Group-IIIA elements (namely, B, Al and Ga) onto alkali metal (AM = Li, Na and K)-supported C6O6Li6 (AM@C6O6Li6) complexes to enhance their NLO response. The AM-C6O6Li6 complexes retained their structural features following interaction with the Group-IIIA elements. Interaction energies as high as -109 kcal mol-1 demonstrated the high thermodynamic stability of these complexes. An exceptional charge transfer behavior was predicted in these complexes, where the electronic density of the Group-III metals shifted toward the alkali metals, making these complexes behave as alkalides. The π conjugation of C6O6Li6 was found to withdraw excess electrons from the Group IIIA metals in these alkalides, which were subsequently transferred to the Group IA metals. The energy gap of the frontier molecular orbitals (FMOs) in the AM-C6O6Li6 complexes was notably reduced upon alkalide formation. UV-visible analysis explicitly showed a bathochromic shift in the alkalides. The first hyperpolarizability (β0) was calculated to confirm the NLO properties of these alkalides. B-C6O6Li6-K exhibited the highest β0 value of 1.75 × 105 au. The vibrational frequency-dependent first and second hyperpolarizability values illustrated an increase in hyperpolarizability at a frequency of 532 nm. A higher n2 value of 8.39 × 10-12 cm2 W-1 was obtained for B-C6O6Li6-Na at 532 nm. These results highlight the promising NLO response of the designed alkalides and their potential applications in the field of optics.

Realizing the effect of s-block metals on a charge transfer crystal of indol-2-one for enhanced NLO responses with efficient energetic offsets

CONTEXT

Due to their unique photophysical properties, organic charge transfer crystals are becoming promising materials for next-generation optoelectronic devices. This research paper explores the impact of s-block metals on a charge transfer crystal of indol-2-one for enhanced nonlinear optical (NLO) responses with efficient energetic offsets. The study reveals that alkali metals can enhance NLO performance due to their free electrons.

METHOD

The Perdew-Burke-Ernzerhof functional of DFT with dispersion correction (D3) was used, and the λmax values ranged between 596 and 669 nm, with the highest value for dichloromethane (DCM). Leveraging the unique properties of metals allowed for the development of nonlinear optical materials with improved performance and versatility. Softness (σ) values provide insight into electron density changes, with higher values indicating a greater tendency for changes and lower values indicating the opposite. The NLO results for the chromophores MMI1-MMI6 show varying linear polarizability (< α0 >) along with their first (β0) and second (γ0) hyperpolarizabilities. Chromophore MMI4 stands out with the highest NLO performance, having two potassium (K) atoms. Its < α0 > , β0, and γ0 values of 4.19, 7.09, and 17.43 (× 10-24 e.s.u), respectively, indicate a significant enhancement in NLO response compared to the other chromophores. The transitions involving (O20)LP → (C3-N5)π* and (O19)LP → (N12-C13)π* exhibit the highest level of stabilization, followed by (O23)π → (C10-C11)π*, while (C6-N12)π → (C6-C7)π* shows the lowest level of stabilization for chromophore MMI4. The present research work is facile in its nature, and it can be helpful for synthetic scientist to design the new materials for uniting crystal properties with metal doping for efficient NLO devices.