Conformationally Restricted Triarylmethanes: Synthesis, Photophysical Studies, and Applications

Abstract

Triarylmethanes, compounds in which the central carbon atom is attached to three aryl rings, have a wide variety of photophysical properties which are utilized in the dye industry and also in the development of novel fluorescent tags and biomarkers. The aryl rings attached to the central carbon atom of the parent molecule triphenylmethane can freely rotate. Bridging the aryl rings of triarylmethanes with heteroatoms or through bonds decreases the conformational flexibility enjoyed by the parent molecules. Conformationally restricted triarylmethane (CRT) molecules like 9‐arylxanthenes (oxygen bridging), 9‐arythioxanthenes (sulfur bridging), 9,10‐dihydro,9‐arylacridines (nitrogen bridging), and 9‐arylfluorenes (bridging through C–C bond) have decreased conformational flexibility and display amphihydric behavior which results in benzenoid structure and quinoid structure of these molecules. The quinoid form of these molecules displays very rich photophysical properties which are the subject of this review. These molecules also have widespread utility, and over the last decade, a number of studies have been focused on the synthesis, photophysical properties, and applications of molecules derived from this core structure. Through this review, we intend to give the readers an outlook on the different strategies employed to synthesize these molecules and also provide a broader perspective on the various intriguing properties of these molecules. The applications of these classes of molecules in diverse fields like photocatalysis, chemical biology, pharmaceutical chemistry, and bio‐imaging are discussed. Also, the areas that need to be further developed are highlighted, which may provide a further impetus in the development of this class of molecules.

Coumarin‐Pyronin Hybrid Dyes: Synthesis, Fluorescence Properties and Theoretical Calculations**

“…Depending on the size and steric hindrance of meso-aryl substituent of the targeted xanthene dye, several traditional and exotic synthetic methods are available in the literature. [13] A classification based on the electrophilic or nucleophilic character of the reagent typically used for formal C-9 functionalization of the xanthene core is generally admitted. [14] Surprisingly, the known reactivity of pyronin dyes linked to the marked electrophilic character of their meso-position, has, to our knowledge, never been employed to introduce structural and functional diversity through addition of cyclic C-nucleophiles and subsequent spontaneous or oxidant-mediated re-aromatization.…”

“…In the case of 7methoxy derivative 11, a decent quality and interpretable 1 H NMR spectrum was only obtained after adding 10% of [D1]TFA in CDCl3. Conversely, it was impossible to obtain a good quality 13 C NMR spectrum despite of extended acquisition time on a 600 MHz spectrometer. The purity of each compound (determined through RP-HPLC analyses) was found to be equal to or above 96%, and thus being suitable for an accurate determination of their photophysical properties.…”

Adhesive application on particleboard from natural fibers: A review

“…Among the properties being addressed include, water repellent, crosslinkers, colorants, fillers, and fire retardant. 70 Wood being cellulosic material is highly vulnerable to insects and fungi attacks. Whereas poor water repellency on the wood particles may lead to dimensional instability, fungi as well as insect attack which can eventually compromise the strength properties of the material.…”

“…The essence of these materials is to control and modify the reaction conditions in the particleboard production, and also modify the final product. Among the properties being addressed include, water repellent, crosslinkers, colorants, fillers, and fire retardant 70 . Wood being cellulosic material is highly vulnerable to insects and fungi attacks.…”

Unprecedented Coumarin-Pyronin Hybrid Dyes: Synthesis, Fluorescence Properties and Theoretical Calculations

“…;1 H NMR (500 MHz, CD3OD): d = 7.65 (d,3 JH,H = 9.5 Hz, 1H), 7.58 (d,3 JH,H = 9.1 Hz, 1H), 7.43 (s, 1H), 7.14 (dd, 3 JH,H = 9.6,4 JH,H = 2.5 Hz, 1H), 6.98 (d,4 JH,H = 2.4 Hz, 1H), 6.90 (dd, 3 JH,H = 9.1, 4 JH,H = 2.1 Hz, 1H), 6.83 (d,4 JH,H = 2.1 Hz, 1H), 3.71 (q, 3 JH,H = 7.2 Hz, 4H), 3.39 (q, 3 JH,H = 3.3 Hz, 4H), 2.95 (t,3 JH,H = 6.4 Hz, 2H), 2.85 (t,3 JH,H = 6.3 Hz, 2H), 2.11-1.95 (m, 4H), 1.33 (t,3 JH,H = 7.3 Hz, 6H);13 C NMR (151 MHz, [D6]DMSO): d = 206.5, 160.8, 159.5, 157.9, 157.4, 155.1, 151.0, 146.7, 132.3, 131.7, 121.1, 117.9, 116.6, 114.6, 114.1, 105.3, 96.8, 95.8, 91.1, 56.0, 49.34, 48.8, 45.2, 27.1, 21.0, 20.1, 20.1, 12.5; 19 F NMR (565 MHz, [D6]DMSO): d = -73.9 (s, 3F, CF3-TFA); HPLC (system A): tR = 4.5 min (purity 97% at 260 nm, 97% at 450 nm and 98% at 500 nm); LRMS (ESI+, recorded during RP-HPLC analysis): m/z 522.2 [M + H] + (100), calcd for C32H32N3O54 + 522.2; LRMS (ESI-, recorded during RP-HPLC analysis): m/z 520.2 [M -H] -(100), calcd for C32H30N3O4 -520.2.…”