X-ray, kinetics and DFT studies of photochromic substituted benzothiazolinic spiropyrans

Abstract

Photochromic molecules have the potential to find utility in a wide variety of applications including photoswitchable binding and optical memory. This work explores the relationship between photochromism and structural parameters such as particular bond lengths for this class of compounds for which very few crystal structures have been published. Photochemical kinetics, Density Functional Theory (DFT) and X-ray crystallography were used to study the benzothiazolinic spiropyran 3-methyl-6-nitro-3′-methylspiro-[2H-l-benzopyran-2,2′-benzothiazoline]. A second benzothiazolinic spiropyran 3-methyl-8-methoxy-6-nitro-3′-methylspiro-[2H-l-benzopyran-2,2′-benzothiazoline] was synthesized and subjected to photochemical and computational studies. Selected structural and photochemical data for these, related benzothiazolinic spirooxazines and spiropyrans, and related thiazolidinic spiropyrans are compared. Both benzothiazolinic spiropyrans exhibit photochromic properties that are influenced by substituents, solvent, and temperature. The crystallographic C spiro -O bond distance of 3-methyl-6-nitro-3′-methylspiro-[2H-l-benzopyran-2,2′-benzothiazoline] that has been shown to correlate with photochromic properties is 1.458 Å. The crystallographic C spiro -O bond distance matches that of the structure generated by DFT calculations exactly. The effect of substituents on calculated bond lengths and photochemical parameters was determined. For this class of compounds, both X-ray geometry and DFT optimized geometry may be used to predict photochromism, but not degree of photocolorability.

Efficient Reversible Optical Sensing of Water Achieved through the Conversion of H‐Aggregates of a Merocyanine Salt to J‐Aggregates

“…The absence of a signal for vinylic‐H at δ5.9‐6.2 ppm region indicated the absence of any closed form . The signal due to the N‐CH 3 group, which usually appear in δ2.7‐3.1 ppm region in the closed form, shifted to δ4.24 ppm in the receptor 1 , which again indicated the presence of merocyanine salt form . The signals at δ7.47 ppm, δ7.09 ppm for aromatic protons and δ2.25 ppm for Ph‐CH 3 group indicated clearly the presence of a tosyl moiety.…”

“…The UV‐visible spectra displayed an absorption band in 480–550 nm region (Figure ). The closed form of the spiropyran usually absorbs in the 300–390 nm region with a maximum at ∼365 nm ,. The exposure of UV‐light (365 nm) produces an open colored merocyanine form of the spiropyran with an absorption band in the 450–640 nm region ,.…”

“…The closed form of the spiropyran usually absorbs in the 300–390 nm region with a maximum at ∼365 nm ,. The exposure of UV‐light (365 nm) produces an open colored merocyanine form of the spiropyran with an absorption band in the 450–640 nm region ,. The absence of any band in 300–390 nm region indicated the absence of the closed form of 1 , which further supported the NMR results.…”

Light-controllable linear dichroism in nematics

“…Spiropyrans (SPs) [1] are photochromic materials that have been extensively investigated due to their potential applications in fields such as information recording and processing [including three-dimensional (3D) recording] [2,3], optical memories [4][5][6], molecular devices [7,8], nonlinear device components and optical switches [9][10][11][12][13][14][15], and light-activated drug delivery systems [16]. The stable state of SPs is a non colored, closed molecular form [17], that can be transformed into their merocyanine (MC) state upon UV irradiation.…”

Preparation of the Inclusion Complex-Type Nonlinear Optical Polymer

“…e PM form can revert to the SP form either thermally or photochemically [25][26][27]. Typically, SP is included in polymer matrices to obtain various forms of solid-state photochromic materials to extend its commercial application range [28][29][30].…”