Switching the Cubic Nonlinear Optical Properties of an Electro‐, Halo‐, and Photochromic Ruthenium Alkynyl Complex Across Six States

Abstract

The impending breakdown in Moores law has prompted the search for molecule-based information-processing components such as molecular switches and logic gates. [1] Bistable molecules that afford states possessing distinct linear optical properties (absorbance, fluorescence) and that can be interconverted by chemical, redox, magnetic, or photonic stimuli have attracted considerable interest for Boolean logic operations. [2] In principle, molecular computing could exploit ternary or higher-order digit representations, which would permit smaller device components. "Switchable" molecular properties are also of intense interest for sensor applications. Despite this interest, molecules that can exist in more than two stable and independently addressable states, which could be employed for complex and higher-order logic functions, have been explored significantly less than two-state molecules. One potentially very important procedure to exploit molecular switches is to utilize their cubic nonlinear optical (NLO) properties, [3] and in particular their nonlinear absorption. [4] However, this avenue is also poorly explored and is to date restricted to switching between three states at most, [5,6] although such switching offers 1) the prospect of broadening the available spectral range (and in particular utilizing telecommunications-relevant wavelengths) and 2) the possibility of enhanced spatial control (compared to linear optical switching) because of the higher-order dependence on the intensity of the incident light. Herein we show that a specific binuclear metal alkynyl complex [7] incorporating a functionalized 5,5'-dithienylperfluorocyclopentene (DTE) bridge [8] can afford six stable and switchable states that possess distinct cubic NLO properties. The complex is comprised of independently addressable modules that respond orthogonally to protic (alkynyl ligandQvinylidene ligand), electrochemical (metal-centered redox: Ru II QRu III ), and photochemical (DTE ring-openingQring-closing) stimuli. The six states are interconverted along seven pathways, all of which result in distinct changes to cubic nonlinearity for specific regions of the spectrum. Our results demonstrate that complexes of this type have the potential to be used, among other things, in the construction of multi-input logic gates responding to diverse stimuli across a broad spectral range.The synthesis of the dinuclear ruthenium alkynyl complex oa(II) is depicted in Figure S1 in the Supporting Information. The DTE unit is obtained in the "open" form as its 5,5'diethynyl derivative; the open DTE is thermally stable, and this open form persists through the preparative steps that ultimately afford oa(II). Complete synthetic and characterization details are given in the Supporting Information. Complex oa(II) can be reversibly protonated to the di(vinylidene) complex ov(II), reversibly oxidized to the Ru III complex dication oa(III), and photoisomerized with UV light to the closed alkynyl complex ca(II). Complex ca(II) can be reversibly protonated to cv(II) an...

Two‐Photon Solvatochromism II: Experimental and Theoretical Study of Solvent Effects on the Two‐Photon Absorption Spectrum of Reichardt’s Dye

“…Noteworthy examples are the detection of a narrowing of the CT absorption band in the temperature range of 10-293 K, [66] low-temperature fluorescence, [40,72,73] or room-temperature fluorescence in the subpicosecond regime. [122][123][124][125] Because it turned out that the solvatochromism of DANS was too elusive to gain any unequivocal information, as a good test-bed, we chose RD for its extraordinary negative solvatochromism. Unfortunately, systematic studies of solvent effects on 2PA are rare.…”

“…Earlier studies concern the extension of the general concept of chromism into the domain of spectra of nonlinear absorption and refraction, including reports on nonlinear analogues of electro-, halo-, and photochromism. [122][123][124][125] Because it turned out that the solvatochromism of DANS was too elusive to gain any unequivocal information, as a good test-bed, we chose RD for its extraordinary negative solvatochromism.…”

Durch Dithienylethen‐Einheiten modifizierte Rubyrine

“…Dadurch werden sie zu einer der vielversprechendsten Baueinheiten für die Synthese von organischen photoschaltbaren Materialien und Photospeichern. [13] In der offenen Form sind die beiden Thiophen-Einheiten über eine Cyclopenten-Einheit an der b-Position verknüpft, wodurch das aromatische System aufgrund der Kreuzkonjugation unterbrochen wird. Durch Einwirkung eines äußeren Stimulus kann das DTE in seine geschlossene Form überführt werden.…”

“…Es ist außerdem bemerkenswert, dass die Abstände C4-C2 (1.336 (5) ), C3-C3' (1.325 (5) ) und C2'-C4' (1.336 (5) ) Doppelbindungscharakter aufweisen und damit deutlich von geschlossenen Formen bereits publizierter Moleküle abweichen. [13] Hieraus folgt, dass die Struktur von 1 deutlich rigider ist als die früherer DTE-modifizierter Verbindungen. Bekanntlich ist die Quantenausbeute für die Cyclisierung (F O!C ) von DTE um den Faktor 10-100 hçher ist als die der Cycloreversion (F c!o ).…”

“…Bekanntlich ist die Quantenausbeute für die Cyclisierung (F O!C ) von DTE um den Faktor 10-100 hçher ist als die der Cycloreversion (F c!o ). [13] Da in 1 nur eine DTE-Einheit enthalten ist, sollte die Verbindung leicht zwischen der offenen, nichtaromatischen Form und der aromatischen, geschlossenen 26 p-Elektronenform schaltbar sein.…”