Intra- and Intermolecular Charge Transfer in a Novel Dimer: Cooperatively Enhancing Second-Order Optical Nonlinearity

Abstract

Based on s-indaceno [1,2,3-cd;5,6,7-c′d′]diphenalene (1) consisting of two phenalenyl moieties, the monomer 2 and its dimer 2 2 are designed by boron and nitrogen atoms substituting the central carbon atoms of phenalenyl moieties. Calculated energy decompose analysis (EDA) shows that the orbital interaction for 2 2 possesses a large attractive contribution of −18.31 kcal mol −1 , which is dominated by the π−π stacking interaction between the upper and the lower π-conjugated units. Interestingly, the natural population analysis (NPA) charge and the transition density matrix (TDM) show that both intramolecular charge transfer and intermolecular charge transfer (CT) exist in 2 2 . Further, the first hyperpolarizability (β tot = 4.56 × 10 4 au) of 2 with intramolecular CT is greatly larger than that of reported molecule 3 (5.45 × 10 3 au) with intermolecular CT. Significantly, 2 2 exhibits the largest β tot value to be 1.42 × 10 5 au, which is caused by combining the intra-and intermolecular CT transitions (β x = 1.40 × 10 5 au and β z = 2.27 × 10 4 au). Correspondingly, highest occupied molecular orbital (HOMO) → lowest unoccupied molecular orbital (LUMO) (intramolecular CT) in the low-energy electronic transition of 2 2 is 68%, while HOMO → LUMO + 1 (intermolecular CT) is 18%, which demonstrates that the intramolecular CT effect on the β tot value is stronger than the case of the intermolecular CT effect. The present work might provide rich insight into designing and developing potential second-order optical nonlinearity materials with inter-and intramolecular CT characters.

Room-Temperature Orange-Red Phosphorescence by Way of Intermolecular Charge Transfer in Single-Component Phenoxazine–Quinoline Conjugates and Chemical Sensing

“…Therefore, the search and use of new SCCTCs are of great interest. Recently, few SCCTCs that rely on the self-association of two parts of the same molecule have been developed by utilizing intermolecular CT (I 2 CT) interaction, which could generate white-light emission, − second-order nonlinear effect, and semiconductive behavior. , To the best of our knowledge, such SCCTCs with efficient RTRP emission have not been reported.…”

Stimulating intra- and intermolecular charge transfer and nonlinear optical response for biphenalenyl biradicaloid dimer under an external electric field

“…29 However, it is still a major challenge to rationally design organic NLO materials with intra-and intermolecular CT. Our group has previously published a fascinating report on a NLO material with intra-and intermolecular CT, that upon introducing heteroatoms (boron/ nitrogen) into the aromatic p-extended biradicaloid has shown a significantly large NLO response. 30,31 This poses an interesting question: is there another effective strategy to externally stimulate long-range intra-and inter molecular CT of systems to further control and modulate the electronic properties of the material?…”

Charge-transfer regulated visible light driven photocatalytic H2 production and CO2 reduction in tetrathiafulvalene based coordination polymer gel

“…22b ). Importantly, the transition at 553 nm was observed due to the significant contribution of intermolecular CT from TTF core to [Zn(TPY) 2 ] 2+ unit as shown in Supplementary Table 2 55 . The dominated intermolecular CT transition in Zn-TPY-TTF CPG as compared to TTF-TPY OG is mainly triggered by the planarization of terpyridine ligand, which occurred after the complexation with Zn II ion in CPG 56 .…”