Studies of the Electronic Structure of Metallocene-Based Second-Order Nonlinear Optical Dyes

Abstract

This paper describes a simple orbital picture for understanding the optical transitions and the second-order nonlinear optical response of metallocene-based chromophores of the form metallocene−(π-bridge)−acceptor, and experimental studies to test this model. From a combination of UV photoelectron spectroscopy, cyclic voltammetry, and density functional calculations, it is deduced that the three highest occupied orbitals are little perturbed from the parent metallocenes, that the HOMO-3 is a π-orbital delocalized between the metallocene cyclopentadienyl ring and the unsaturated bridge, and that the LUMO is acceptor based. The lowest energy transition in the UV/visible/near-IR spectra of these compounds is assigned to a metal-to-acceptor transition, while the higher energy transition is attributed to a transition to the acceptor-based LUMO from the delocalized HOMO-3 orbital. The variations in oscillator strength can be rationalized by considering the low-energy transition as borrowing intensity from the high-energy transition. Stark spectroscopy confirms that large dipole moment changes are associated with both transitions, as expected from our assignment. These dipole moment changes indicate that, according to the perturbation theory-derived expression for the first hyperpolarizability, β, both transitions contribute significantly to the observed optical nonlinearity.

Negative Solvatochromism of Ferrocenyl Methine Dyes

“…In general, the electronic absorption of these dyes show one band between 325 and 395 nm assigned to π-π* transition and another one at a longer wavelength between 509-521 nm due to metal-to-ligand charge transfer (MLCT) and no absorption observed for d-d transition unless it is covered by the broad LMCT band. These assignments are based on theoretical results reported by Barlow et al [3] and other experimental findings [7][8][9][10] . The two bands are strongly influenced by the nature of the acceptor group as well as by the polarity of the solvent.…”

“…We reported the preparation and characterization of new ferrocenylbased methines with an end capped with different electron-withdrawing groups [1][2][3] . Here, we report the synthesis of ferrocenyl methine dyes by the condensation of ferroce-3-carboxaldehyde with active methylene compounds under Konovengel conditions to afford a new methine dyes with absorption maximum in the visible region (Scheme 1).…”

“…From the large shifts observed for 1a, we conclude that it has larger polarazability compared with 1b-1d due cyano electron withdrawing groups. The negative bathochromic shift is certainly due to opposite in sign between the dipole moments of the ground and excited states [3] . Compounds 1b-1d showed red as well as blue shift from both transition (π-π* and MLCT).…”

DFT Study on Nonlinear Optical Properties of 7,10,12 Vertexes Ferradicarbollide Sandwich Complexes

“…ML y ] (M 代表金属, L 代表配体)中 [17] , 二茂铁及其衍生 物因具有很好的 NLO 性质而备受关注 [18] . Todd 等 [19] 于 [32] : [33,34] , 因 此 采 用 PBE1PBE/6-31G* (Fe 采用 SDD 基组)方法计算分子的吸 收光谱.…”

2-Aza-1,3-butadiene ligands for the selective detection of Hg2+ and Cu2+ ions

“…The electronic absorption spectra show the typical absorption bands corresponding to the naphthalene or pyrene 13 chromophore subunits in the region 265-347 nm for 6 and 8 and 235-391 nm for 7 and 9. Additionally, the ferrocenyl derivatives 6-9 also exhibit another weaker low-energy (LE) absorption band in the region 484-501 nm which is assigned to a ferrocenyl-based metal-to-ligand charge transfer process (MLCT) 14 (Table 1). By contrast, the UV-vis spectra of 10 and 11 showed a LE band, centered at 409 nm attributed to the aza-bridge, along with the typical pyrene absorption bands.…”