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The nonlinear optical responses of carbon nanohoop derivatives increase significantly with the increasing number and the length of π-bridges.

To compare homoleptic [2]catenanes and single rings consisting of gold(i) thiolates, the geometric and electronic structures, absorption spectra, binding energy, interaction energy and composition of intramolecular forces were studied theoretically.

DFT and TD-DFT calculations were performed to turn conventional non-TADF units into high-lying reverse intersystem crossing D–A–D-type TADF emitters.

Two planar-like molecules, 1 and 2, were designed and characterized via the introduction of BNB or NBN bonds into the planar phenalenyl.

Spin-unrestricted DFT and spin-unrestricted TDDFT calculations were performed to systematically investigate the correlation between the electron donating ability of donors and photophysical properties in D–A luminescent radicals.

The present work aims to study the effect of an external electric field as well as arrangement of donor–acceptor groups on the second-order nonlinear optical (NLO) properties of push–pull systems. The first hyperpolarizabilities (βtot) of acceptor–donor molecules (m-AD and p-AD regioisomers) are investigated based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as the electron-acceptor and benzodithiophene (BDT) as the electron-donor. Calculated results show that the βtot value (7.49 × 103 a.u.) of p-AD is larger than that (1.03 × 103 a.u.) of m-AD. Furthermore, we investigate that the external electric fields (along the positive or the negative directions of x-axis, Fx and F−x) regulate the NLO properties of the p-AD. (1) As Fx increases, the βtot values of p-AD are gradually decreased to 0 (Fx ranging from 0 to 30 × 10−4 a.u.). (2) As F−x increases, the βtot values are sharply increased (F−x ranging from 0 to −30 × 10−4 a.u.). It is worth noting that the βtot value is increased to 3.70 × 104 a.u. (F−x = −30 × 10−4 a.u.). Moreover, the evolutions of the simulated UV-Vis absorption spectra can well explain the trends of βtot values under an external electric field. The present work not only provides a deeper understanding of the relationship between structure and NLO properties, but also expands electric field-induced switchable NLO materials.

An interesting biphenalenyl biradicaloid (IDPL) dimer consisting of both-middle superimposed phenalenyls and both-end nonsuperimposed phenalenyls has been synthesized, and has attracted intensive research interest due to its intra- and intermolecular interactions and semiconductive characteristics. It is significant that under regulation of the external electric field the directional charge transfer (CT) can produce attractive properties. In the present work, the structure and electronic properties of the IDPL dimer under an external electric field (along the horizontal Fx or the vertical Fz directions) are explored, and the following properties determined: (i) as the horizontal Fx increases, the intramolecular CT becomes larger, which induces the intermolecular CT of the IDPL dimer. (ii) In contrast, as the vertical Fz increases, the large intermolecular CT gives rise to the intramolecular CT of the IDPL dimer. (iii) More importantly, the external electric field effectively regulates and controls the first hyperpolarizability (βtot) of the IDPL dimer. Compared with the vertical Fz, the horizontal Fx induces a larger first hyperpolarizability (βtot = 5.48 × 105 a.u.). Furthermore, the application of a uniform external electric field (Fx,y,z) to the IDPL dimer was investigated to define the external electric field direction of the material application. The βtot values were increased with increasing of the uniform Fx,y,z. Our study provides an effective strategy for developing high-performance NLO materials by tuning the external electric field, and could be of significance for application in switch devices.

A series of diradical π-dimers 2 with interesting pancake-shaped 2e/24c π-π bonding character were designed and investigated based on the famous phenalenyl (PLY) π-dimer with 2e/12c π-π bonding character. The position of stronger interaction between two layers of radicals was found by the Wiberg bond index (WBI) maximum component. Further, the different contributions of the interaction energy were analyzed quantitatively by energy decomposition analysis (EDA). Among these new diradical π-dimers, 2180 has the smallest layer distance and the largest interaction between two layers of radicals. The unusual PLY analogues can provide new insights into the unique features of two-electron/multicenter (2e/mc) π-π bonding.