Organometallic Complexes for Nonlinear Optics. 30.¹ Electrochromic Linear and Nonlinear Optical Properties of Alkynylbis(diphosphine)ruthenium Complexes

Abstract

A combination of cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, time-dependent density functional theory (TD-DFT), and Z-scan measurements employing a modified optically transparent thin-layer electrochemical (OTTLE) cell has been used to identify and assign intense transitions of metal alkynyl complexes at technologically important wavelengths in the oxidized state and to utilize these transitions to demonstrate a facile electrochromic switching of optical nonlinearity. Cyclic voltammetric data for the ruthenium(II) complexes trans-[RuXY(dppe)(2)] [dppe = 1,2-bis(diphenylphosphino)ethane, X = Cl, Y = Cl (1), Ctbd1;CPh (2), 4-Ctbd1;CC(6)H(4)Ctbd1;CPh (3); X = Ctbd1;CPh, Y = Ctbd1;CPh (4), 4-Ctbd1;CC(6)H(4)Ctbd1;CPh (5)] show a quasi-reversible oxidation at 0.50-0.60 V (with respect to ferrocene/ferrocenium 0.56 V), which is assigned to the Ru(II/III) couple. The ruthenium(III) complex cations trans-[RuXY(dppe)(2)](+) were obtained by the in situ oxidation of complexes 1-5 using an OTTLE cell. The UV-vis-NIR optical spectra of 1(+)-5(+) contain a low-energy band in the near-IR region ( approximately 8000-16 000 cm(-)(1)), in contrast to 1-5, which are optically transparent at wavelengths < 22 000 cm(-)(1). TD-DFT calculations have been applied to model systems trans-[RuXY(PH(3))(4)] [X = Cl, Y = Cl, Ctbd1;CPh, or 4-Ctbd1;CC(6)H(4)Ctbd1;CPh; X = Ctbd1;CPh, Y = Ctbd1;CPh or 4-Ctbd1;CC(6)H(4)Ctbd1;CPh] to rationalize the optical spectra of 1-5 and 1(+)-5(+). The important low-energy bands in the electronic spectra of 1(+)-5(+) are assigned to the promotion of an electron from either a chloride p orbital or an ethynyl p orbital to the partially occupied HOMO. These absorption bands have been utilized to demonstrate a facile switching of cubic nonlinear optical (NLO) properties at 12 500 cm(-)(1) (corresponding to the wavelength of maximum transmission in biological materials such as tissue) using the OTTLE cell, the first electrochromic switching of molecular nonlinear refraction and absorption, and the first switching of optical nonlinearity using an electrochemical cell.

Multistate Redox‐Active Metalated Triarylamines

“…The 16-electron species [RuCl(dppe) 2 ]-[PF 6 ] [14] was generated from cis-[RuCl 2 (dppe) 2 ] [15] (1) by chloride abstraction using NaPF 6 and subsequently treated with 4-ethynyl-N,N-diphenylaniline to form the vinylidene complex trans-[Ru(C=CH-4-C 6 H 4 NPh 2 )Cl(dppe) 2 ][PF 6 ] (2, Scheme 1). Deprotonation of 2 by using triethylamine then affords the mono-alkynyl complex trans-[Ru(CϵC-4-C 6 H 4 NPh 2 )Cl(dppe) 2 ] (3), previously prepared in similar yield by direct treatment of 4-ethynyl-N,N-diphenylaniline with 1, without isolation of the intermediate vinylidene complex.…”

“…[4] One reason is because oxidation of such compounds can "switch on" absorptions at low energy, thus significantly affecting the third-order NLO behavior. [5][6][7][8][9] We have reported carbonrich organometallics with three accessible redox states as possible multistate linear optical and NLO switches; in particular, we described the introduction of [(η 5 -C 5 Me 5 )(dppe)-Fe(CϵC-4-C 6 H 4 CϵC)Ru(dppe) 2 ] [dppe = 1,2-bis(diphenylphosphanyl)ethane] fragments into both linear and threefold symmetric branched aryleneethynylene architectures; the heterodinuclear fragment permits switching between three states. [10,11] As a continuation of these studies, we now report (i) replacement of the organoiron [Fe(dppe)(η 5 -C 5 HCϵC-4-C 6 H 4 NPh 2 and (HCϵC-4-C 6 H 4 ) 3 N are irreversible processes.…”

Charge localization on a redox-active single-molecule junction and its influence on coherent electron transport

“…We chose this particular system because it was used in previous conductance measurements 22,23 as a monomer of chains -albeit with different anchor groups -where it was found that depending on the chain length either coherent transport or electron hopping is observed 22 . In addition spectroscopic and quantum chemical studies on similar Ru complexes [24][25][26][27][28] suggest that this molecular species offers the possibility to easily link two carbon-rich chains to each other for the formation of reversible redox systems [29][30][31] with distinct optical transition properties 32,33 , thereby serving as a starting point for the investigation of chains with multiple redox active centers 27 . In contrast to Ref.…”

Where organometallics and dendrimers merge: the incorporation of organometallic species into dendritic molecules

“…The combination of these NLO properties and the demonstrated reversible electrochemical behavior of the Ru-acetylide functions [84] have also been investigated in terms of a possible reversible modulation of the optical properties of these species. The trimeric RuCl species undergoes reversible metal-centered redox processes (Ru II/III ) in solution.…”