Organometallic Complexes for Nonlinear Optics. 43. Quadratic Optical Nonlinearities of Dipolar Alkynylruthenium Complexes with Phenyleneethynylene/Phenylenevinylene Bridges

Abstract

The syntheses of trans-[Ru(4,4'-C[triple bond]CC(6)H(4)C[triple bond]CC(6)H(4)NO(2))Cl(dppe)(2)] (19) and the systematically varied complexes trans-[Ru(4,4',4''-C[triple bond]CC(6)H(4)X(2)C(6)H(4)Y(2)C(6)H(4)NO(2))Cl(L(2))(2)] [L(2) = dppe, X(2) = C[triple bond]C, Y(2) = (E)-CH=CH (12), C[triple bond]C (18); L(2) = dppe, X(2) = (E)-CH=CH, Y(2) = C[triple bond]C (14), (E)-CH=CH (16); L(2) = dppm, X(2) = C[triple bond]C, Y(2) = (E)-CH=CH (13); L(2) = dppm, X(2) = (E)-CH=CH, Y(2) = C[triple bond]C (15), (E)-CH=CH (17)] are reported, the latter being donor-bridge-acceptor complexes varying in bridge composition by replacement of yne with E-ene linkages, together with their cyclic voltammetric data, linear optical, and quadratic nonlinear optical response data. Ru(II/III) oxidation potentials increase on replacing yne linkage by E-ene linkage at the phenylene adjacent to the metal center, and on replacing dppe by dppm co-ligands. The low-energy optical absorption maxima occur in the region 20,400-23,300 cm(-1) and are metal-to-ligand charge-transfer (MLCT) in origin; these bands undergo a blue-shift upon pi-bridge lengthening by addition of phenyleneethynylene units, and on replacing E-ene linkages by yne linkages. Time-dependent density functional theory calculations on model complexes have suggested assignments for the low-energy bands. The optical spectra of selected oxidized species contain low-energy ligand-to-metal charge transfer (LMCT) bands centered in the region 9760-11,800 cm(-1). Quadratic molecular nonlinearities from hyper-Rayleigh scattering (HRS) studies at 1064 nm reveal an increase in the two-level-corrected beta(0) value on pi-bridge lengthening, a trend that is not seen with beta values because of the blue-shift in lambda(max) for this structural modification. Replacing yne linkages by E-ene linkage at the phenylene adjacent to the metal center or dppm co-ligand by dppe results in an increase in beta and beta(0) values. In contrast, quadratic molecular nonlinearities by HRS at 1300 nm or electric field-induced second-harmonic generation (EFISH) studies at 1907 nm do not afford clear trends.

Synthesis, Optical, Electrochemical, and Theoretical Studies of Dipolar Ruthenium Alkynyl Complexes with Oligo(phenylenevinylene) Bridges

“…The results from cyclic voltammetric studies on Ru4 , Ru6 , and Ru8 (Figure S81) reveal a fully reversible oxidation process for each complex at about 0.5 V, a potential similar to those for previously reported trans ‐[Ru(C≡CR)Cl(L 2 ) 2 ] complexes lacking acceptor groups (see, for example, Refs. ), together with an irreversible nitro‐centred reduction at about −1 V (Table ). Ruthenium complexes with 4‐nitrophenylethynyl ligands show oxidation potentials of about 0.7 V (see Ru1 , Table ), reducing on π‐system lengthening (see Ru2 and Ru3 , Table ).…”

“…For example, the experimental absorption maxima of Ru4 , Ru6 , and Ru8 exist in a narrow spectral region (23 500 cm −1 –24 000 cm −1 ) and they are significantly blue‐shifted compared to the bands in the UV/Vis spectra of shorter compounds. Similarly, a blue‐shift in the lowest‐energy band is seen on proceeding from Ru2 to Ru3 . The C s point group imposed during the aforementioned calculations does not allow the π‐bridge phenyl groups to alter the idealized coplanar arrangement, and thus this may not represent the statistically averaged structures relevant under laboratory conditions.…”

“…Despite the strong interest in functionalized OPVs and in the NLO properties of metal alkynyl complexes, there have thus far only been limited studies of the NLO properties of stilbenes end‐functionalized by (a) metal alkynyl unit(s), and only one study of a similarly functionalized OPV (containing a di(phenylenevinylene) unit, the shortest OPV, although octupolar and dendritic phenylenevinylene‐containing complexes have been reported) . We report herein the syntheses of end‐functionalized OPV alkynyl complexes incorporating tri‐, penta‐, and hepta(phenylenevinylene) groups, together with studies exploring their electrochemical and linear and quadratic nonlinear optical properties, comparisons to previously reported shorter homologues, and theoretical studies rationalizing the experimental observations.…”

Linear Optical, Quadratic and Cubic Nonlinear Optical, Electrochemical, and Theoretical Studies of “Rigid‐Rod” Bis‐Alkynyl Ruthenium Complexes

“…Application of suitable potentials to solutions of selected complexes in dichloromethane afforded clean isosbestic points during the formally Ru II to Ru III oxidation process; a representative example is given in Figure , and pertinent results are collected in Table . Previous theoretical studies have assigned the lowest energy band (7000–15 000 cm −1 ) in the spectra of related oxidized complexes as ligand‐to‐metal charge transfer (LMCT) in character . Examination of the spectral data of the oxidized complexes in this study affords several conclusions.…”

“…Low‐energy linear optical behavior is expected to be significantly affected by planarity of the π bridge, as shown by previous related studies . We assessed the influence of the orientation of the alkynyl ligands with respect to the metal center, as well as the relative orientation of the planes of the two alkynyl ligands, on the low‐lying linear optical data in 16M , the smallest bis‐alkynyl complex in the set.…”