Assembling of Perylene, Naphthalene, and Pyromellitic Diimide-Based Materials and Their Third-Order Nonlinear Optical Properties

Electronic and Nonlinear Optical Properties of B(III)-Submonoazaporphyrin-π-Diimide Compounds: A Density Functional Theory Study

Three hypothetical complexes were designed using diimides (PMDI, NTCDI, and PTCDI) as the acceptor unit and B(III)-submonoazaporphyrin (1) as the donor unit. These complexes have smaller HOMO-LUMO energy gaps (3.39-3.96 eV) than pristine 1 (6.61 eV). Further, the energy gap can be tuned by changing the number of benzene rings of these diimides. Remarkably, these proposed complexes possess considerable first hyperpolarizabilities (β0) (4865-6921 a.u.), and the regularity of the β0 values remained the same in the gas phase and toluene solvent conditions. There is an inverse relationship between the energy gap and the polarizability/first hyperpolarizability. In addition, absorption spectra, frontier molecular orbitals, and hole electron distributions were obtained using time-dependent density functional theory calculations to emphasize the relationship between structure and properties. Ultraviolet-Visible absorption spectra reveals that all complexes show satisfying IR working regions. Further analysis of the first hyperpolarizability density reveals the nature of the excellent NLO properties of the studied systems. This study can provide valuable insights for the development of potential high-performance NLO molecules.

Theoretical study on porphyrin arch-tapes of carbonyl-inserted seven-membered rings with high nonlinear optical properties

Porphyrin tapes have attracted extensive attention because their fully conjugated π-networks act as nonlinear optical (NLO) materials. A family of Ni(II) and Zn(II) porphyrin arch-tapes that are connected by varying bridge (B) ligands (meso-meso β-β doubly linked dimer 1, meso-meso β-β β-β triply linked dimer 3, methylene-inserted dimer 2 and trimer 5, carbonyl-inserted dimer 4, trimer 6, and Zn(II) trimer 7) have been synthesized by a density functional theory (DFT) method. The results show that carbonyl-inserted arch-tapes significantly enhance second hyperpolarizability (γ), indicating that the remarkably contorted structure incorporated seven-membered ring(s) directly affect their NLO properties of our focus. Moreover, the electronic absorption spectra calculated for all studied complexes with time-dependent DFT theory (TDDFT) predict that carbonyl-inserted complex 4 contributes to a red-shift of the Q-band (160 nm) for the meso-meso β-β doubly linked complex 1. The third-order NLO responses and the electron transition properties strongly depend on the nature of the bridge (B) ligand, which means that an active involvement of the carbonyl group presents an advantage for its application in NLO materials.

Optical and Electrochemical Properties of a Photosensitive Pyromellitic Diimide Derivative of Cymantrene

Photochemical properties of symmetrical pyromellitic diimide containing two cymantrenyl fragments at two nitrogen atoms were studied with IR, NMR, UV-vis, ESI-MS, and cyclic voltammetry. It was found that new unstable chelates are formed during photolysis. At the same time, the CO ligand dissociates from two Mn(CO)3 fragments during photoexcitation, which dramatically changes the electronic and redox properties of the molecule compared to the cymantrene derivative containing one imide fragment. Photolysis leads to a color change from light yellow to green. DFT calculations confirmed the possibility of the formation of complexes due to the loss of one or two CO ligands from manganese atoms. The results obtained with variation of photolysis conditions demonstrated the hemilabile character of the Mn-O=C(imide) bond. On addition of external ligands, the color and electrochemical properties changed, which is promising for the use of this complex as a sensor for small molecules.

Effects of Atypical Hydrogen Bonds and π-π Interactions on Nonlinear Optical Properties: Dimers of Triangular Structures Based on Perylene, Naphthalene, and Pyromellitic Diimides

Nonlinear optical (NLO) materials have become important materials in the field of high-speed optical devices due to the changes in light absorption and refraction caused by the photoelectric field. Compounds tend to exist as aggregates rather than single molecules, so intermolecular interactions are crucial to the nature of aggregates. Therefore, to study the effects of intermolecular interactions on nonlinear optical properties, we use a dimer simplified model and adopt the methods of controlling variables, which are the different intermolecular interactions resulting from the different stacking patterns of dimers based on the same monomer structures (2PMDI-1NDI and 2NDI-1PDI). It is found that compared with dimers involving π-π interactions, dimers involving C-H···O interactions have shorter intermolecular distances, larger intermolecular interaction energies, and smaller highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps. Moreover, the C-H···O interactions are more conducive to the intermolecular charge transfers and more beneficial for increasing the nonlinear optical response values of aggregates with respect to π-π interactions. This work provides an important basis for the influence of intermolecular interactions on nonlinear optical properties.