Effect of the Coordination to the “Os₃(CO)₁₁” Cluster Core on the Quadratic Hyperpolarizability oftrans-4-(4‘-X-styryl)pyridines (X = NMe₂,t-Bu, CF₃) andtrans,trans-4-(4‘-NMe₂-phenyl-1,3-butadienyl)pyridine

Abstract

Coordination to the "Os 3 (CO) 11 " cluster core of substituted styrylpyridines such as trans-4-(4′-NMe 2 -styryl)pyridine (L 1 ), trans-4-(4′-t-Bu-styryl)pyridine (L 2 ), trans-4-(4′-CF 3 -styryl)pyridine (L 3 ), or trans,trans-4-(4′-NMe 2 -phenyl-1,3-butadienyl)pyridine (L 4 ) produces an enhancement of their quadratic hyperpolarizability, β EFISH , measured by the solution-phase dc electric-field-induced second harmonic (EFISH) generation method. This effect is due either to a red-shift of the intraligand charge-transfer (ILCT) transition upon coordination (when the substituent in para position is a strong electron donor) or to a metal-to-ligand chargetransfer (MLCT) transition (when the substituent is a strong electron acceptor). In the latter case the quadratic hyperpolarizability has a negative sign, due to the negative value of ∆µ eg . Therefore the "Os 3 (CO) 11 " cluster core displays an ambivalent acceptor or donor role. Some of the complexes investigated in this study show significant values (between 500 × 10 -48 and 900 × 10 -48 esu) of the product µβ 0 .

Second Order Nonlinear Optical Properties of 4-Styrylpyridines Axially Coordinated to A4 ZnII Porphyrins: A Comparative Experimental and Theoretical Investigation

“…While the electron-donating ligand L2 was purchased, the electron-accepting ligand L1 was designed and synthesized with the purpose of combining their electronic effect with the abovementioned electron-deficient and electron-rich porphyrins. L1 was obtained by adapting an elsewhere reported procedure for similar stilbazole-based ligands [10] (see Supporting Information). Finally, L1 and L2 were coupled with the four Zn II porphyrins TPP, TBP, TNP, and TFP by refluxing CH 2 Cl 2 solutions of the proper components from 3 h to 72 h depending on the specific combinations between porphyrin and ligands.…”

“…The spectra in CHCl 3 solution are reported in the Supporting Information ( Figures S6-S10), while the corresponding experimental data are summarized in Table 1. L1 and L2 show one electronic absorption band due to a π→π* internal transition for the former, whereas a n→π* ILCT transition from the -NMe 2 donor end to the pyridine ring for the latter [10,40,41].…”

“…In particular, when the metal center is Zn II , a remarkable enhancement of the second order NLO response is recorded due to its inductive acceptor strength and its Lewis acid properties [5][6][7][8]. 4-styrylpyridines have been coordinated to a variety of metal fragments, including carbonyl moieties [4,9] and metal carbonyl clusters [10]. Through coordination, the modulus of their quadratic hyperpolarizability β (which is the figure of merit of the second order NLO response) increases significantly, with a sign that depends on the nature of the substituent in para position.…”

Porphyrins for Second Order Nonlinear Optics (NLO): An Intriguing History §

“…It has been reported [32,35,36] that, by coordination of E-stilbazoles to a metal center, a significant increase of their second order NLO response is produced, depending on the nature of the substituent in the para position of the aromatic ring, and by the metal ion acting as a Lewis acid [32,35]. Therefore, a donor group gives a positive and enhanced value of β λ , while an electron acceptor produces a negative value if the metal center is quite soft.…”

Zinc(II) as a Versatile Template for Efficient Dipolar and Octupolar Second-Order Nonlinear Optical Molecular Materials §

“…The µβ 1.91 (EFISH) value of 4,4 -trans-NMe 2 -C 6 H 4 CH=CHC 5 H 4 N (CHCl 3 , 5 × 10 −4 M) [41] increases by a factor of 2.3 upon coordination to the "Zn(CH 3 CO 2 ) 2 " moiety [38], which is mainly due to the large increase of the dipole moment (complex 1, Table 1). In fact, the quadratic hyperpolarizability is quite similar, which is in agreement with the irrelevant red-shift upon coordination of the stilbazole ILCT (∆λ max = 2 nm) [38].…”