Changes in the luminescence emission of α,β-unsaturated acrylonitrile derivatives: morphology, polymorphism and solvent effect

Abstract

We report an interesting and clear property-structure relationship between the emission wavelength and the morphologies of samples separated by evaporation using a sublimator and a solvent. The compounds are (Z)-3-(4-(dimethylamino)phenyl)-2-(pyridin-4-yl)acrylonitrile Z-DMPyACN (I) and (Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-2-yl)acrylonitrile Z-DPPyACN (II). I exhibits strong emission in the solid state, but not in a solution, whereas II exhibits emission in a solution and as a solid. Characterization by single-crystal X-ray crystallography showed that the Z-DMPyACN polymorph (Ii) has a monoclinic unit cell with a = 7.0445(2); b = 17.1474IJ5); c = 10.9776(4) Å, and β = 107.251IJ4)°and is found in the space group P2 1 /c with Z′ = 1. The orange crystal habit and color are different from the structure reported, (Z′ = 2, block and yellow). The Ii luminescence displayed an absorbance maximum at λ max = 427 nm and an emission maximum at λ em = 555 nm. From the Z-DPPyACN II evaporation in the sublimator, three solids were recovered, featuring emission wavelengths that were dependent on the size of the particles (nanoparticles) rather than on the single-crystal structure. The IIg, IIy, and IIo powders showed emission maxima at λ em = 546, 558, and 607 nm, respectively. Characterization was carried out by UV-vis, fluorescence and 1 H-NMR in different polarity solvents, as well as SCXRD, PXRD and SEM.

One‐ and Two‐Component Organogels Containing Cyanostilbene without any Auxiliary Substituents

“…The 4− N, N‐dimethylamine group in both molecules were observed to be in co‐planar conformation with the conjugated system with a dihedral angle of −179.38. Further, the bond length, bond angles, and torsion angles are compared with reported structure and found to be almost similar . Crystal packing in 3 is mainly stabilized by N⋅⋅⋅H−C interaction (Table S3) between the nitrogen of 4‐pyridyl ring and methyl group of 4‐N, N‐dimethyl amino group of the neighboring molecule (Figure b).…”

“…Further, the bond length, bond angles, and torsion angles are compared with reported structure and found to be almost similar. [14] Crystal packing in 3 is mainly stabilized by N···HÀ C interaction (Table S3) between the nitrogen of 4-pyridyl ring and methyl group of 4-N, Ndimethyl amino group of the neighboring molecule (Figure 5b). These interactions extended along ab plane and further stabilized by weak CÀ H···π (2.9 Å) and CÀ H···N interactions (C15AÀ H···N2; 2.69 Å) between two 4-pyridyl rings and 4dimethylamino group (stilbene 3A) and nitrile group (stilbene 3) giving a 2D sheet architecture.…”

Solution and Solid-State Photophysical Properties of Positional Isomeric Acrylonitrile Derivatives with Core Pyridine and Phenyl Moieties: Experimental and DFT Studies

“…Crystals of Ia and Ib were obtained in solvent 1 (DMSO) and 6 (EtOAc) and also in DMF ( I c). The results from SCXRD showed that Ia and Ib were not polymorphic structures, but they exhibited differences in fluorescence emission of their crystals; this phenomenon had already been observed [ 51 , 52 , 53 ]. The Mercury software [ 76 ] showed that the molecular structures obtained in EtOAc ( 6 ) compared with DMSO ( 1 ) are conformers, but the crystals obtained from DMSO and DMF were not, implying a solvent polarity effect.…”

“…The optical properties can also be altered by substituents located in various positions around the molecular structure [ 41 , 43 , 44 ]. Especially, the optical properties of compounds containing a pyridine ring and with α-cyanostilbenes with dimethylamine, diphenylamine, halogen atoms and N -ethylcarbazole substituents have been reported [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. It has been established that molecules are not emitters in solution (SCQ) [ 54 , 55 ], which prompted us to question why are such compounds not emitters?…”

Experimental and Theoretical Insights into the Optical Properties and Intermolecular Interactions in Push‐Pull Bromide Salts

“…Compound IIa crystallized in the orthorhombic Pbcn space group (refcode: AWEGEQ) with one molecule in the asymmetric unit . In order to understand the effect of quaternization of the pyridine nitrogen atom in I–II , a detailed structural comparison of I–II and their precursor structures ( Ia–IIa ),, has been performed. As shown in Figure (a), the structure of I is well overlaid with both forms of Ia .…”