Solvatochromism and Reversible Solvent Exchange Phenomena in Solvatomorphic Organic Chromophore Crystals

Abstract

Solvatomorphs or solvates are common in pharmaceutical compounds, and solvatochromism is often reported in solution. The present study reports eight solvates of (Z)-3-(3-hydroxy-4-methoxy phenyl)-2-(4-nitrophenyl) acrylonitrile, a π-conjugated push−pull organic chromophore. The solvates containing (i) chlorobenzene, (ii) ethyl-acetate, (iii) 1,4dioxane, (iv) acetone, (v) acetonitrile, (vi) N,N-dimethylformamide, (vii) N-methyl-2pyrrolidine, and (viii) dimethyl sulfoxide as solvents in their crystal lattices display the solvatochromism effect. All the solvates and the parent form are systematically characterized using spectroscopic, crystallization, thermal analysis, single-crystal X-ray diffraction techniques, and structural analysis. The solvatomorphs reported here are either non-isostructural or have a low degree of isostructurality, except for one pair for which a three-dimensional isostructurality is observed. The structural stabilities of the solvates are correlated with their molecular packing, crystal voids, and thermal properties. Moreover, the possible mechanism behind the solvatochromism and the reversible solvent exchange phenomena have been explored. This report is one of the rarest series of solvatomorphs exhibiting reversible solvent exchange properties and solvatochromic effect both in crystal and solution. Such studies are crucial for the dye and pharmaceutical industries dealing with various solvents and the formulation of drugs in solvated forms, respectively.

Solvates and Polymorphs of Baloxavir Marboxil: Crystal Structure and Phase Transformation Study

“…It has been observed that solvents can easily escape from crystals over time and solvates are transformed into solvent-free forms. Considering that S MA and S 2‑THF are channel solvates, and solvents are weakly bound to their crystal lattice, we speculate that the solvents in the solvates can be replaced by other solvent molecules and new forms may form. − Thus, four solvated crystals were placed in various solvent vapor atmospheres to check whether there is solvent vapor-induced phase transformation . As shown in Table , S MA , S 2‑THF , and S DIOX transformed with each other under the corresponding solvent vapor.…”

Color Packing Polymorphism in an Organic Chromophore

“…9−13 Often, polymorphs are categorized based on their morphology, color, stability, molecular conformation, packing, and presence of different solvents. 3,14 Occasionally, two or more crystal forms can coexist at the same temperature, pressure, or solvent conditions, and these are called concomitant polymorphs. 3,5,15,16 Conformational polymorphs 17,18 can also exhibit color polymorphism.…”

“…Their systematic screening concluded that polymorphs occur frequently in molecular crystals. However, it is predominantly discovered in compounds with pharmaceutical interests, , and its existence in organic materials with exotic properties is scarce. − Often, polymorphs are categorized based on their morphology, color, stability, molecular conformation, packing, and presence of different solvents. , Occasionally, two or more crystal forms can coexist at the same temperature, pressure, or solvent conditions, and these are called concomitant polymorphs . ,,, Conformational polymorphs , can also exhibit color polymorphism. 5-Methyl-2-[(2-nitrophenyl)­amino]-3-thiophenecarbonitrile, popularly known as ROY, is used for the synthesis of olanzapine, an antipsychotic drug, is a well-studied case of conformational color polymorphs .…”

Solvatochromism of new tetraphenylethene luminogens: integration of aggregation-induced emission and conjugation-induced rigidity for emitting strongly in both solid and solution state

“…[47][48][49][50] Molecules with low dipole moments in the ground state but signicant dipole moments in the excited state, oen due to ICT, exhibit a shi towards longer wavelengths (bathochromic shi) as solvent polarity increases. [49][50][51] This shi occurs because more polar solvents provide excellent stabilization for the dipolar excited state. [52][53][54] Recently, the polarity-dependent emission of substituted TPE derivatives was reported.…”

“…7,46 Solvatochromism refers to the changes in the absorption or emission spectrum of a molecule upon altering the polarity of the solvent. [47][48][49][50] Molecules with low dipole moments in the ground state but signicant dipole moments in the excited state, oen due to ICT, exhibit a shi towards longer wavelengths (bathochromic shi) as solvent polarity increases. [49][50][51] This shi occurs because more polar solvents provide excellent stabilization for the dipolar excited state.…”