Search

This study reports the crystal structures of potassium and cesium salts of adenine (K-adenine and Cs-adenine) from the perspective of the interaction of alkali cations with purine nucleobases. Unlike previously-known guanine salts, both K-adenine and Cs-adenine are anhydrous, with the counter ions (K+ and Cs+) directly coordinating to the ring nitrogens of adenine anions. In both structures, the crystal packing is predominantly determined by cation–anion interactions, with additional stabilization through hydrogen-bonding of neighbouring adenines. Attempts to crystallise either the cesium salt of guanine or the sodium salt of adenine were unsuccessful. To explain this trend, quantum-chemical calculations were performed to rationalise the preferences of sodium, potassium, and cesium cations to coordinate either with water or adenylate/guanylate anions. The exchange energies of cation–anion complexes reveal that sodium cations exhibit a preference for water or guanylate coordination via oxygen, while cesium cations prefer adenylate coordination via nitrogen functions, avoiding water interaction. Potassium exhibits an intermediate trend. Overall, this research offers insights into interactions between alkali-cations and organic anions, aiding the development of new crystalline compounds and co-crystals. [ABSTRACT FROM AUTHOR]

A novel category of asymmetric boron chromophores with the attachment of two BF2 moieties denoted as BOPAM has been successfully synthesized via a one‐pot three‐step reaction starting from N‐phenylbenzothioamide. This synthetic route results in the production of [a] and [b]benzo‐fused BOPAMs along with post‐functionalization of the [a]benzo‐fused BOPAMs. The photophysical properties of these compounds have been systematically investigated through steady‐state absorption and fluorescence emission measurements in solvents at both ambient and cryogenic temperatures, as well as in the solid state. Computational methods have been employed to elucidate the emissive characteristics of the benzo‐fused BOPAMs, revealing distinctive photophysical attributes, including solvent‐dependent fluorescence intensity. Remarkably, certain BOPAM derivatives exhibit noteworthy photophysical phenomena, such as the induction of off‐on fluorescence emission under specific solvent conditions and the manifestation of intermolecular charge transfer states in solid‐state matrices. Through post‐functionalization strategies involving the introduction of electron‐donating groups onto the [a]benzo‐fused BOPAM scaffold, an intramolecular charge transfer (ICT) pathway is activated, leading to substantial fluorescence quenching via non‐radiative decay processes. Notably, one [a]benzo‐fused BOPAM variant exhibits a pronounced fluorescence enhancement upon exposure to acidic conditions, thereby underscoring its potential utility in pH‐sensing applications. [ABSTRACT FROM AUTHOR]

Disubstituted isothiazolo[4,3-b]pyridines are known inhibitors of cyclin G-associated kinase. Since 3-substituted-7-aryl-isothiazolo[4,3-b]pyridines remain elusive, a strategy was established to prepare this chemotype, starting from 2,4-dichloro-3-nitropyridine. Selective C-4 arylation using ligand-free Suzuki-Miyaura coupling and palladium-catalyzed aminocarbonylation functioned as key steps in the synthesis. The 3-N-morpholinyl-7-(3,4-dimethoxyphenyl)-isothiazolo[4,3-b]pyridine was completely devoid of GAK affinity, in contrast to its 3,5- and 3,6-disubstituted congeners. Molecular modeling was applied to rationalize its inactivity as a GAK ligand. [ABSTRACT FROM AUTHOR]

The title compound, C27H20N4O3S, crystallizes in the monoclinic system, space group P21/n, with Z = 4. The global shape of the molecule is determined by the orientation of the substituents on the central 4H-1,2,4-triazole ring. The nitrophenyl ring, phenyl ring, and naphthalene ring system are oriented at dihedral angles of 82.95 (17), 77.14 (18) and 89.46 (15)°, respectively, with respect to the triazole ring. The crystal packing features chain formation in the b-axis direction by S...O interactions. A Hirshfeld surface analysis indicates that the highest contributions to surface contacts arise from contacts in which H atoms are involved. [ABSTRACT FROM AUTHOR]

A new family of unsymmetrical boron chromophores chelated with two BF2 units, named BOPAM, has been developed via a one‐pot, three‐step reaction starting from commercially available thioamides via i) conversion to amidrazones, ii) condensation with pyrrole aldehydes, and iii) boron chelation. This synthetic pathway has been proven to be highly efficient, having a broad substrate tolerance and giving the BOPAM products high yield. Notably, some of the BOPAM dyes show interesting photophysical properties with fluorescence quantum yields up to 0.98 in toluene. A fine‐tuning of their emissive properties has been attained through tailored molecular design strategies guided by in‐depth computational investigations. Tailored substitution with electron‐donating groups at the BOPAM ring leads to the opening of a non‐radiative decay channel involving a dark state and consequently a significant quenching of the fluorescence. The study is complemented by exhaustive steady‐state and time‐resolved spectroscopic measurements. [ABSTRACT FROM AUTHOR]

The molecular and crystal structure of (E)-2-[(benzo[d]thiazol-2-ylimino)- methyl]-5-(diethylamino)phenol (C18H19N3O2S, Et2N-Bz) and its unexpected reaction product with triphenylborane, 2,2-diphenyl-1,3-dioxa-2-borata-1,2-dihydronaphthalene [systematic name: N,N-diethyl-2,2-diphenyl-2H-1,3λ³,2λ4-benzodioxaborinin-7-amine, C23H24BNO2, (I)] are described. For Et2N-Bz, the hydroxyl group is involved in an intramolecular hydrogen bond with the imino nitrogen atom and the C N bond displays an E configuration. The crystal packing is characterized by layers of inversion dimers parallel to the (101) plane and chains of molecule in the a-axis direction formed through C--H⋯O interactions. Complex (I) crystallizes with two molecules (A and B) in the asymmetric unit, which differ in the orientation of the ethyl groups. The 1,3- dioxa-2-borata-1,2,3,4-tetrahydronaphthalene ring displays a slight envelope conformation with the boron atom as the flap. In the crystal packing, chains of alternating A and B molecules formed by C--H⋯O hydrogen bonds run in the b-axis direction. The UV--vis absorption and emission properties of the compounds are discussed and their aggregation-induced emission properties are further investigated. [ABSTRACT FROM AUTHOR]