The variability of hydrogen-bonded supramolecular assemblies in crystalline picrates prepared from ferrocenyl-substituted β-aminoalcohols

Influence of molecular structure on the photoluminescence of 2-methyl benzimidazolium picrate: a new fluorescent material

This work reports the structural and photo luminescent characterization of the 2-methyl benzimidazolium picrate salt for the first time. This new material exhibits the π-π stacking of aromatic rings involving the benzimidazolium cation and picrate anion, which is additionally supported with a rare n→π interaction as well as with the extended networks of intermolecular hydrogen bonds in the solid state. The FT-IR and UV characterizations further support the solid state structural features of the salt. However, the spectroscopic results reveal that the stacking of ion pairs, which is observed in the solid state, is not maintained in solution. The DSC result indicates that the material is stable under ambient temperature conditions. Interestingly, upon photo excitation at 325 nm in the solid state, the material shows an unusual red emission around 615 nm, which is probably attributed to the supramolecular stacked nature of the ion pairs, along with a usual picrate centered green emission at 530 nm. However, the fluorescence measurement in solution, wherein the stacking of ion pairs are not maintained, shows only a single peak at lower wavelength. These observations highlight the influencing role of the supramolecular stacking interactions on the photoluminescence of the material, due to which, a chemical sensing action may be envisaged.

(R)-N-(Ferrocenylmethyl)-1-hydroxy-3-phenylpropan-2-aminium (E)-but-2-enoate

The crystal structure of the title salt, [Fe(C₅H₅)(C₁₅H₁₉NO)](C₄H₅O₂), consists of discrete ammonium and carboxyl­ate ions, which associate into infinite chains parallel to [100] by means of N—H⋯O and O—H⋯O inter­actions. These chains are further cross-linked into a three-dimensional network by additional C—H⋯O contacts and by offset π–π stacking inter­actions of inversion-related aromatic rings [centroid–centroid distance = 3.7040 (14) Å]. The mol­ecular parameters of the ionic components are in no way unexpected, the geometry of the ammonium cation being similar to that found in other structurally characterized salts obtained from N-ferrocenylmethyl β-amino­alcohols. The (E)-but-2-enoate anion consists of two approximately planar subunits, viz the delocalized carboxyl­ate unit and the butenyl group (the latter being planar within ca. 0.002 Å), which are mutually rotated by 30.3 (4)°.

The Knoevenagel product of indolin-2-one and ferrocene-1,1'-dicarbaldehyde

Indolin-2-one (oxindole), (I), undergoes a Knoevenagel condensation with ferrocene-1,1'-dicarbaldehyde, (II), to afford the title complex 3,3'-[(E,E)-ferrocene-1,1'-diyldimethylidyne]diindolin-2-one dichloromethane disolvate, [Fe(C(28)H(20)N(2)O(2))]·2CH(2)Cl(2), (IV). The structure of (IV) contains two ferrocene complex molecules in the asymmetric unit and displays, as expected, intermolecular hydrogen bonding (N-H···O=C) between the indolin-2-one units. Intermolecular π-π stacking interactions are also observed.