Hyperpolarizabilities Of Complexes Research Articles

Theoretical design of alkaline earthides M+(36 adz) Be− (M+ = V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) with excellent nonlinear optical response and ultraviolet transparency

A novel series of alkaline earthides containing eight complexes based upon 36adz complexant are designed by placing carefully transition metals (V–Zn) on inner side and alkaline earth metal outer side of the complexant i.e., M+(36adz) Be− (M+ = V, Cr, Mn, Fe, Co, Ni, Cu and Zn). All the designed compounds are electronically and thermodynamically stable as evaluated by their interaction energy and vertical ionization potential respectively. Moreover, the true nature of alkaline earthides is verified through NBOs and FMO study, showing negative charge and excess electrons on alkaline earth metal respectively. Furthermore, true alkaline earthides characteristics are evaluated graphically by spectra of partial density state (PDOS). The energy gap (HOMO -LUMO gap) is very small (ranging 2.95 eV–1.89 eV), when it is compared with pure cage 36adz HOMO-LUMO gap i.e., 8.50 eV. All the complexes show a very small value of transition energy ranging from 1.68eV to 0.89eV. Also, these possess higher hyper polarizability values up to 2.8 x 105au (for Co+(36adz) Be−). Furthermore, an increase in hyper polarizability was observed by applying external electric field on complexes. The remarkable increase of 100fold in hyper polarizability of Zn+(36adz) Be− complex is determined after application of external electric field i.e., from 1.7 x 104 au to 1.7 x 106 au when complex is subjected to external electric field of 0.001 au strength. So, when external electric field is applied on complexes it enhances the charge transfer, polarizability and hyper polarizability of complexes and proves to be effective for designing of true alkaline earthides with remarkable NLO response.

Effect of π-conjugate units on the ferrocene-based complexes: Switchable second order nonlinear optics controlled by redox stimuli

The control of rotational motion, using an external impulse (such as redox), has been intensively pursued as nonlinear optics switch. Four redox responsive ferrocene-based actuators with varied π-conjugated units have been systematically investigated by the density functional theory. The open structures of these complexes with antiparallel orientation of both π-conjugated units are due to the large charge repulsion effect, while the closed forms are stabilized by the intramolecular π–π stacking interactions.The rotational motion can be triggered by reduction process preferentially centered on the π-conjugated units. The polarizabilities and first hyperpolarizabilities of complexes [3]closed2+ and [4]closed2+ are significant enhanced, which are respectively related to the electronic spatial extent and intramolecular interlayer charge transfer occurred between two respective π-conjugated units. Overall, the present work shows that one can design the molecular nonlinear optical switches characterized by a large contrast varying from zero to a large value along the reversible transformations.

On the Origins of Large Interaction-Induced First Hyperpolarizabilities in Hydrogen-Bonded π-Electronic Complexes

In this article we elucidate the origins of interaction-induced linear and nonlinear electro-optic properties of model hydrogen-bonded π-electronic complexes. In particular we report on contributions due to various interaction energy terms to excess dipole moments (Δμ), electric dipole polarizabilities (Δα), and first hyperpolarizabilities (Δβ), focusing on the latter. The analysis of intermolecular interaction-induced electric properties is performed for selected model systems including quasi-linear dimers of urea, diformamide, 4-pyridone, 4-nitroaniline, and the complex of hydrogen fluoride with nitroacetylene. The nature of intermolecular interactions as well as of the Δμ and Δα is very similar in all studied complexes. However, partitioning of Δβ into physically well-defined components reveals that the origins of this term, the magnitude of which is often comparable to the hyperpolarizabilities of isolated monomers, are different in each case. Our results indicate that, even though hydrogen bonding usually diminishes the nonlinear response of interacting species, the first hyperpolarizability of complexes with the nitro group acting as a proton acceptor is substantially increased, essentially due to field-induced changes of electrostatic interactions between subsystems. However, in the remaining complexes the origins of Δβ are much more involved. Even though at large intermolecular separations the origins of interaction-induced electric properties are essentially due to the field-induced electrostatic and induction interactions, in the vicinity of van der Waals minimum the overlap effects cannot be neglected since they may substantially alter the predicted excess properties or even determine their magnitude and sign. On the other hand the Δβ contribution due to dispersion interactions is usually negligible. Interestingly, the values of interaction-induced first hyperpolarizability in some cases depend strongly on the intermolecular separation in the vicinity of equilibrium geometry.