Visible Photosensitization of trans-Styrylpyridine Coordinated to fac-[Re(CO)₃(dcbH₂)]⁺: New Insights

Abstract

A strategic methodology has been developed to effectively synthesize the fac-[Re(CO) 3 (dcbH 2 )(trans-stpy)] + complex, where dcbH 2 = 2,2′-bipyridine-4,4′-dicarboxylic acid and trans-stpy = trans-4-styrylpyridine, which has been designed to efficiently absorb visible light. The complex exhibits outstanding trans-to-cis photoisomerization with 436 nm irradiation (Φ trans→cis = 0.50 ± 0.03), in contrast to the photochemical behavior previously reported in the literature (

Spectroscopic Study of the E/Z Photoisomerization of a New Cyrhetrenyl Acylhydrazone: A Potential Photoswitch and Photosensitizer†

“…The singlet MLCT excited state ( 1 MLCT) undergoes a fast intersystem crossing to the triplet excited state ( 3 MLCT) (27), which can transfer its energy to a triplet intraligand excited state ( 3 IL) localized on the photoswitchable fragment, finally producing a photoisomerization reaction (28). For example, fac-tricarbonyl Re(I) fragments have been used to promote the photoisomerization of stilbene-like and azobenzene ligands in the visible spectral region (29)(30)(31)(32)(33)(34). These compounds showed a remarkable cis ⇌ trans photoreversibility with quantum yield values as high as Φ trans?cis = 0.17-0.65 range and Φ cis?trans = 0.16-0.26 range, offering a new strategic approach to designing molecular switches (32,33).…”

Emission Switching in the Near-Infrared by Reversible Trans–Cis Photoisomerization of Styrylbenzene-Conjugated Osmium Terpyridine Complexes

“…Thus, the H 9 and H 10 protons experienced an upfield shift [Δδ­(H 9 ) = 0.60 ppm and Δδ­(H 10 ) = 0.61 ppm] accompanied by a decrease in the values of the coupling constant (from ∼16 to ∼12 Hz). The adjacent H 7 , H 8 , H 11 , and H 12 protons also underwent a measurable amount of upfield shift [Δδ­(H 7 ) = 0.12 ppm, Δδ­(H 8 ,H 11 ) = 0.09 ppm, and Δδ­(H 12 ) = 0.11 ppm] upon irradiation of up to 10 h. Such a change in the NMR spectra clearly goes in favor of the isomerization (t–t → t–c) behavior. ,, …”

“…Upon irradiation with 490 nm light, we found a gradual decrease in the intensity of peaks for the protons across the double bonds (H 9 and H 10 ) and the adjacent protons (H 7 , H 8 , H 11 , and H 12 ). Simultaneous evolution, together with gradual intensification of the peaks for the said protons, was found in the upfield region upon isomerization with time (H 7′ = 8.41 ppm, J = 7.5 Hz; H 8′ = 8.01 ppm, J = 7.5 Hz; H 9′ = 7.17 26,35,36 We tried to achieve the reverse isomerization process by keeping the isomerized form of the complexes, but it was found to be extremely slow. Further we tried irradiating the isomerized solution again by light of different wavelengths and found that irradiation with UV light of 280 nm can lead to the reverse isomerization process irrespective of solvents, although the process is very sluggish compared with the forward process.…”

“…Molecular species capable of reversibly altering their physicochemical properties in response to external stimuli are very useful with regard to their potential applications in photoswitches and molecular memory. − Light is one of the most convenient sources among the stimuli for operating molecular devices because it is a clean source and can be easily applicable to any state of the material and any wavelength of choice can be selected to excite a specific molecular unit within a very short time domain. In order to develop suitable switching molecular devices, the photoisomerization behaviors of different organic systems have been thoroughly studied. − By contrast, reports on the photoisomerization studies of metal complexes are comparatively less. − Recently, photoisomerization studies of metal complexes (Re, Ru, and Ir) having stilbene types of ligands are being investigated. − Coordination complexes have been extensively used as materials in photovoltaic, optoelectronic, and photonic devices as well as in sensors. − The usefulness of the complexes over organic counterparts is due to their great tunability of the optoelectronic and photoredox properties, which can be regulated in a desired manner upon variation of the metal as well as the organic counterpart. − …”

Low-cost photo-switches based on stilbene-appended Zn(II)–terpyridine complexes

“…Optically stimulated reversible trans-cis isomerization of stilbene appended heavier transition metal complexes (particularly Re, Ru, Ir and Pt) were thoroughly investigated by different research groups [46][47][48][49][50][51][52][53][54][55][56]. The results of these investigations laid the foundation for the construction of effective photo molecular switches.…”