N-[2-(2,2-Dimethylpropanamido)- pyrimidin-4-yl]-2,2-dimethyl- propanamide n-hexane 0.25-solvate hemihydrate

The asymmetric unit of the title compound, C₁₄H₂₂N₄O₂·0.25C₆H₁₄·0.5H₂O, contains two independent molecules of 2,4-bis(pivaloylamino)pyrimidine (M) with similar conformations, one water molecule and one-half n-hexane solvent molecule situated on an inversion center. In one independent M molecule, one of the two tert-butyl groups is rotationally disordered between two orientations in a 3:2 ratio. The n-hexane solvent molecule is disordered between two conformations in the same ratio. The water molecule bridges two independent M molecules via O-H...O, N-H...O and O-H...N hydrogen bonds into a 2M·H₂O unit, and these units are further linked by N-H...N hydrogen bonds into chains running in the [010] direction. Weak C-H...O interactions are observed between the adjacent chains.peerReviewe

Topology switch between AIE and ACQ: a balance of substituents

Intermolecular interactions appearing in solution, aggregates and solid state are known to affect the photophysical properties of fluorophores, leading either to emission quenching or to emission enhancement upon aggregation. The novel strategy for the aggregation-induced fluorescence change based upon the subtle balance of the intermolecular and intramolecular charge transfer in the benzothiazole derivatives is presented here, leading to the extremely bright aggregates of the compounds dark in solution or vice versa. The introduction of the two different mild substituents into the fluorophore core results in two regioisomers exhibiting the same crystal packing, but extremely different behavior upon aggregation. Such an approach opens a simple way of controlling the AIE/ACQ behavior of small molecules in the wide range of FQY values

Tuning the Electronic Properties of the Dative N-B Bond with Associated O-B Interaction: Electron Localizability Indicator from X-Ray Wavefunction Refinement

Despite the immense growth in interest in difluoroborate dyes, the nature of the interactions of the boron atom within the N-BF2-O kernel is not yet fully understood. Herein, a set of real-space bonding indicators is used to quantify the electronic characteristics of the dative N-B bond in difluoroborate derivatives. The atoms-in-molecules (AIM) partitioning scheme is complemented by the electron localizability indicator (ELI-D) approach, and both were applied to experimental and theoretical electron-density distributions (X-ray constrained wavefunction fitting vs. DFT calculations). Additionally, Fermi orbital analysis was introduced for small DFT models to support and extend the findings for structures that contain BF2

Two (E)-2-({[4-(dialkylamino)phenyl]- imino}methyl)-4-nitrophenols

The slow evaporation of analytical NMR samples resulted in the formation of crystals of (E)-2-({[4-(dimethyl­amino)­phenyl]­imino}­methyl)-4-nitro­phenol, C15H15N3O3, (I), and (E)-2-({[4-(diethyl­amino)­phenyl]­imino}­methyl)-4-nitrophenol, C17H19N3O3, (II). Despite the small structural difference between these two N-salicylidene­aniline derivatives, they show different space groups and diverse mol­ecular packing. The mol­ecules of both compounds are close to being planar due to an intra­molecular O-H...N hydrogen bond. The 4-alkyl­amino-substituted benzene ring is inclined at an angle of 13.44 (19)° in (I) and 2.57 (8)° in (II) with respect to the 4-nitro-substituted phenol ring. Only very weak inter­molecular [pi]-[pi] stacking and C-H...O inter­actions were found in these structures.peerReviewe

The Influence of the pi-Conjugated Spacer on Photophysical Properties of Difluoroboranyls Derived from Amides Carrying a Donor Group

International audienceA series of difluoroboranyls derived from amides carrying a variable pi-conjugated spacer between the electron-donating (D) and electron-accepting (A) groups was synthesized and characterized with H-1, B-11 C-13, N-15, and F-19 NMR, electronic absorption, fluorescence spectroscopies, and first-principle calculations. The D-to-A distance in the series varied from 1.5 to 4.5 angstrom, causing bathochromic shifts of both the absorption and fluorescence maxima by more than 120 and 213 nm, respectively. These trends are rationalized by quantum-mechanical calculations that allow for quantification of the charge transfer distance. Theoretical calculations were also performed to determine the vibronic couplings and thus to reproduce the experimental band shapes

Synthesis and Photophysical Properties of Novel Donor-Acceptor N-(Pyridin-2-yl)-Substituted Benzo(thio)amides and Their Difluoroboranyl Derivatives

quantum yield than its oxygen counterpart. The fluorescence quantum yield is much higher upon formation of theThe unprecedented N-pyridin-2-yl substituted benzo(thio)amides were prepared and subsequently converted into the cyclic difluoroboranyl (BF2) derivatives. Mass spectrometry, multinuclear NMR, IR, and elemental analysis confirmed the structure of these compounds. UV/vis and fluorescence spectroscopy as well as first-principle calculations were used to study their properties. For the first time, the influence of both the O/S replacement and presence/absence of the BF2 moiety on the photophysical properties of compounds exhibiting charge transfer properties were examined experimentally and theoretically. We show that the sulfur-containing compound has a much smaller emission difluoroboranyl complex