Synthesis, crystal structure, and Hirshfeld surface analysis of 3-ferrocenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine.

A key step towards utilizing polynuclear metal-based systems in magnetic device applications involves the careful design of ligands. This strategic planning aims to produce metal assemblies that exhibit some kind of 'switch' mechanism. Towards this end, a ligand that incorporates a redox-active functional group (ferrocene) is reported. This communication presents the multi-step synthesis, characterization (1H and 13C NMR), and structural analysis (single-crystal X-ray diffraction and Hirshfeld surface analysis) of 3-ferrocenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine, [Fe(C5H5)(C13H11N4)]. Supra-molecular features, including π-π stacking and hydrogen bonding are qu-anti-fied, while a database search reveals the unique combination of mol-ecular moieties, which offer future opportunities for studies to involve simultaneous Lewis acid and base coordin-ation.

Structures, Phase Behavior, and Fluorescent Properties of 3-Phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine and Its ZnCl2 Complex.

The synthesis of the asymmetric ligand 3-phenyl-1-(pyridin-2-yl)-1H-pyrazol-5-amine (L1) and its single-crystal X-ray structure are reported. L1 displays crystallographic symmetry (orthorhombic, Pccn) higher than its molecular symmetry (point group C1) and also displays supercooling, with a difference in the melting and solidification points of over 100 °C. Upon complexation with ZnCl2, L1 engages in both primary cation and secondary anion coordination via hydrogen bonding, and the complex exhibits a room-to-low-temperature single crystal-to-crystal phase transition. The ZnCl2 complex becomes a birefringent fluid mixed with crystalline domains at high temperatures, as detected by polarized optical microscopy. Examination of the photoluminescence properties showed that the emission intensity increased and a pronounced bathochromic shift was observed in the emission maximum upon going from solution to the solid state, for both the ligand and complex, consistent with aggregation-induced emission behavior.

Synthesis of Emissive Heteroacene Derivatives via Nucleophilic Aromatic Substitution.

A synthetic approach for preparing a variety of heterocyclic tetrahydropentacene derivatives via nucleophilic aromatic substitution reactions of bidentate nucleophiles and tetrafluoroterephthalonitrile was developed. X-ray crystallography of several products revealed that the compounds containing oxygen and nitrogen heteroatoms are highly planar and engage in π-stacking, while the compounds containing sulfur are bent and do not stack as effectively. The compounds were also highly emissive, and the heteroatom had a significant impact on the emission and electrochemical properties.

Synthesis and Characterization of Liquid-Crystalline Tetraoxapentacene Derivatives Exhibiting Aggregation-Induced Emission.

A series of new tetrakis(dialkoxyphenyl) dicyanotetraoxapentacene derivatives (1 a-c) were prepared by reaction of the appropriate terphenyl diols with tetrafluoroterephthalonitrile in good yields. Compounds 1 b and 1 c, which bear hexyloxy and decyloxy side chains, exhibited columnar hexagonal mesophases, as shown by polarized optical microscopy, variable-temperature powder X-ray diffraction, and differential scanning calorimetry. Single-crystal X-ray diffraction of methoxy-substituted 1 a revealed that the dicyanotetraoxapentacene core is highly planar, consistent with the notion that these molecules are able to stack in columnar mesophases. A detailed photophysical characterization showed that these compounds exhibit aggregation-induced emission in solution, emission in nonpolar solvents, weak emission in polar solvents, and strong emission in the solid state both as powder and in thin films. These observations are consistent with a weakly emissive charge-transfer state in polar solvents and a more highly emissive locally excited state in nonpolar solvents.

The tipping point of the inert pair effect: experimental and computational comparison of In(I) and Sn(II) bis(imino)pyridine complexes.

The autoionization reaction of neutral bis(imino)pyridine and SnX2 led to three compounds [{ArN[double bond, length as m-dash]CPh}2(NC5H3)]SnX(+)SnX3(-) (Ar = 2,6-(2,5-(t)Bu2C6H3), X = Cl, Br; Ar = 2,6-(2,6-Me2C6H3), X = Cl) which display, within the same species, cations and anions possessing Sn(ii) centers. Computational analysis compared the ligated Sn(ii) cations with bis(imino)pyridine In(i) complexes that showed unprecedented weak metal-ligand covalent interactions, consistent with the In(i) 5s(2) electrons remaining as an inert nonbonding pair. Analysis of the metal-ligand bonding indicates that the chloride ligand of the Sn(ii) complex induces promotion of the metal 5s(2) electron pair to a stereochemically active hybridized orbital, which, in turn, allows strong coordination of the bis(imino)pyridine to Sn.