Synthesis, Characterization and Photochromic Studies of Spirooxazine‐Containing 2,2′‐Bipyridine Ligands and Their Rhenium(<scp>i)</scp> Tricarbonyl Complexes

Ko, Chi‐Chiu; Wu, Lixin; Wong, Keith Man‐Chung; Zhu, Nianyong; Yam, Vivian Wing‐Wah

doi:10.1002/chem.200305485

Cited by 93 publications

(47 citation statements)

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“…Much work has focused on organic systems, in which high‐energy UV excitation is required for the intramolecular photosensitization of the photochromic spirooxazine moiety. It was only quite recently that examples of transition‐metal complexes involving photosensitization of the photochromic behavior through excitation of lower‐energy metal‐to‐ligand charge transfer (MLCT) bands in the visible region were reported 6e,h,i,p–s…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

Tam

Wong

et al. 2011

Chemistry A European J

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A series of multifunctional platinum(II) bipyridine complexes were designed, synthesized, and characterized by (1)H NMR, fast atom bombardment mass spectrometry (FAB-MS), and elemental analysis. Their electrochemical and photophysical properties were investigated. The photochromic properties of the spironaphthoxazine-containing complexes were also studied. Some of these complexes were shown to be capable of forming stable thermoreversible metallogels in organic solvents. In contrast to typical thermotropic organogels and metallogels, one of the complexes could form metallogels in dodecane and is very stable towards external stimuli. The photochromic activation parameters for the bleaching reaction of a representative spironaphthoxazine-containing complex in a dodecane gel were determined through kinetic studies at various temperatures. Lamellar liquid-crystalline behavior was also observed in one of the complexes, and the liquid-crystalline properties were studied by thermogravimetry analysis (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), variable-temperature X-ray diffraction (XRD), and variable-temperature infrared (IR) spectroscopy.

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Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

Tam

Wong

et al. 2011

Chemistry A European J

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“…More impressively, the decay becomes much faster in chloroform (1.80 10 À1 s À1 ; Table 2). The experimental data were fitted with Equation (1), [15] in which A 0 , A 1 , and A are the initial absorbance, infinite absorbance, and absorbance at t(s), respectively.…”

Section: Resultsmentioning

confidence: 99%

Aromaticity‐Controlled Thermal Stability of Photochromic Systems Based on a Six‐Membered Ring as Ethene Bridges: Photochemical and Kinetic Studies

Yang

Xie

Zhang

et al. 2012

Chemistry A European J

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Three photochromic compounds--2-butyl-5,6-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]-1 H-benzo[de]isoquinoline-1,3(2 H)-dione (BTE-NA), 4,5-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]benzo[c][1,2,5]thiadiazole (BTA), and BTTA, which contain naphthalimide, benzothiadiazole, and benzobisthiadiazole as six-membered ethene bridges with different aromaticities--were systematically studied in solution, sol-gel, and single-crystal states. They exhibit typical photochromic performance with considerably high cyclization quantum yields. BTE-NA, BTA, and BTTA form a typical donor-π-acceptor (D-π-A) system with significant intramolecular charge transfer (ICT) between HOMO and LUMO upon excitation, thus realizing the fluorescence modulation by both photochromism and solvatochromism. The three ethene bridges with different degrees of aromaticity can provide a systematic comparison of the thermal stability evolution for their corresponding closed forms (c-BTE-NA, c-BTA, and c-BTTA). c-BTE-NA shows first-order decay in various solvents from cyclohexane to acetonitrile. c-BTA only shows first-order decay in polar solvents such as chloroform, whereas it is stable in nonpolar solvents like toluene. In contrast, the less aromatic property of BTTA gives rise to its unprecedented thermal stability in various solvents even at elevated temperatures in toluene (328 K). Moreover, the small energy barrier between the parallel and antiparallel conformers allows the full conversion from BTTA to c-BTTA. In well-ordered crystal states, all three compounds adopt a parallel conformation. Interestingly, BTTA forms a twin crystal of asymmetric nature with interactions between the electron-rich oxygen atom of the methoxy group and the carbon atom of the electron-deficient benzobisthiadiazole moiety. This work contributes to the understanding of aromaticity-controlled thermal stability of photochromic systems based on a six-membered ring as an ethene bridge, and a broadening of the novel building blocks for photochromic bisthienylethene systems.

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“…Unlike the trans-cis photoisomerization, in which the triplet reaction pathway has been well documented [1,3], the photochromic ring-opening reaction of spirooxazines absorption band of these complexes, where the free ligand (SOPY) does not absorb, suggested an intramolecular photosensitization of the spirooxazine by the MLCT excited state [19]. As all these complexes only show LC phosphorescence instead of the typical MLCT phosphorescence, the photochromic ring-opening reaction was proposed to be initiated with an efficient intramolecular energy transfer from the 3 MLCT state to the reactive 3 SOPY state, followed by ringopening reaction.…”

Section: Photosensitization Of Spirooxazine-containing Ligandsmentioning

confidence: 99%

“…Extension of this work to a series of spirooxazine-containing bipyridine ligands (L1-L4) and their tricarbonyl rhenium(I) complexes (Figure 2.7a) was reported [19]. However, the photochromism of the spirooxazine-containing bipyridine ligands could not be sensitized by the 3 MLCT excited state of the rhenium(I) complexes as the 3 MLCT state to the 3 LC state triplet-triplet energy transfer was disfavored by the lower-lying 3 MLCT state (166-188 kJ mol −1 , estimated from the phosphorescence of these complexes) compared to the 3 LC state of the spirooxazine (210-225 kJ mol −1 ) [20].…”

Section: Photosensitization Of Spirooxazine-containing Ligandsmentioning

confidence: 99%

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Photochromic Transitional Metal Complexes for Photosensitization

Yam

2016

Photochromic Materials: Preparation, Properties and Applications

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IntroductionPhotochemical reactions of most organic compounds (except those with carbonyl substituent) occur predominantly at the lowest-lying singlet excited state (S 1 ). This is attributed to the very inefficient intersystem crossing (ISC) from the singlet to the triplet state due to its spin-forbidden nature. In contrast, triplet excited-state photochemistry of carbonyl-containing organic compounds are well reported because the singlet-triplet energy splitting of these types of compounds are much smaller, leading to the effective population of their triplet excited state on light absorption [1]. To tackle the inefficient ISC, the photoreactivity of an organic compound derived from the triplet state can be achieved by using a triplet photosensitizer, through which light is absorbed by the photosensitizer and energy is transferred from its triplet excited state to the acceptor organic molecule to populate the triplet excited state (Figure 2.1). To achieve photosensitization, which bypasses the reactivity from singlet excited states, the photosensitizer must possess long-lived and higher-lying triplet (T 1 ) energy than the acceptor organic molecule for efficient energy transfer but lower-lying singlet state (S 1 ) for selective photoexcitation of the photosensitizer (Figure 2.1).In the organic photochromic systems, even though the photochromism is originated from different reaction mechanisms such as reversible trans-cis photoisomerizations as well as the reversible photoinduced ring-opening and ring-closing reactions, most of these reactions are derived from the excited singlet state [2]. Studies on the photochromic reactivity of azo compounds [3], stilbenes [3], spiropyrans [4], and spirooxazines [5] via the triplet excited-state pathway achieved by intermolecular photosensitization with organic photosensitizers have also been reported in the literature [3][4][5]. Along with the rapid development of phosphorescent metal polypyridine complexes in the 1970s, diffusion-controlled intermolecular sensitization of photochromic reactions of stilbenes with the triplet excited state of tris(bipyridyl)ruthenium(II) [6] and tricarbonyl rhenium(I) bipyridine [8] complexes has been demonstrated. The

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Synthesis, Characterization and Photochromic Studies of Spirooxazine‐Containing 2,2′‐Bipyridine Ligands and Their Rhenium(i) Tricarbonyl Complexes

Cited by 93 publications

References 64 publications

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

Aromaticity‐Controlled Thermal Stability of Photochromic Systems Based on a Six‐Membered Ring as Ethene Bridges: Photochemical and Kinetic Studies

Photochromic Transitional Metal Complexes for Photosensitization

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