Abstract
The monocation product of the oxidative condensation-cyclization between two mol-ecules of pyridine-2-carbaldehyde and one mol-ecule of CH3NH2·HCl in methanol, 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium, was isolated in the presence of metal ions as bis-[2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridin-2-ium] tetra-iodo-cadmate, (C13H12N3)2[CdI4], (I), and the mixed chloride/nitrate salt, bis-[2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridin-2-ium] 1.5-chlor-ide 0.5-nitrate trihydrate, 2C13H12N3 +·1.5Cl-·0.5NO3 -·3H2O, (II). Hybrid salt (I) crystallizes in the space group P21/n with two [L]2[CdI4] mol-ecules in the asymmetric unit related by pseudosymmetry. In the crystal of (I), layers of organic cations and of tetra-halometallate anions are stacked parallel to the ab plane. Anti-parallel L + cations disposed in a herring-bone pattern form π-bonded chains through aromatic stacking. In the inorganic layer, adjacent tetra-hedral CdI4 units have no connectivity but demonstrate close packing of iodide anions. In the crystal lattice of (II), the cations are arranged in stacks propagating along the a axis; the one-dimensional hydrogen-bonded polymer built of chloride ions and water mol-ecules runs parallel to a column of stacked cations.
Highlights
Organic–inorganic hybrid salts have maintained steady research interest in materials science (Dıaz & Corma, 2018)
The serendipitous discovery of the formation of 2-methyl-3(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, L+, in the oxidative condensation–cyclization of 2-pyridinecarbaldehyde (2-PCA) and CH3NH2ÁHCl in methanol and the following preparation of the fluorescent [L]2[ZnCl4] hybrid salt in the presence of Zn2+ ions prompted our research on organic
We aimed to study the effect of the halide variation on the resulting hybrid salt structure
Summary
Organic–inorganic hybrid salts have maintained steady research interest in materials science (Dıaz & Corma, 2018). The serendipitous discovery of the formation of 2-methyl-3(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, L+, in the oxidative condensation–cyclization of 2-pyridinecarbaldehyde (2-PCA) and CH3NH2ÁHCl in methanol and the following preparation of the fluorescent [L]2[ZnCl4] hybrid salt in the presence of Zn2+ ions prompted our research on organic–. Heterocycles with the imidazo[1,5-a]pyridine skeleton show prominent photophysical properties (Hutt et al, 2012) and have the potential to be used in optoelectronic technology Their incorporation in the halometallate structure may improve the mechanical properties, chemical resistance, thermal stability, etc. The new organic–inorganic hybrid [L]2[CdI4] (I) involving the in situformed L+ cation has been prepared in the reaction system: 2-PCA – CH3NH2ÁHCl – CdI2 – KI – CH3OH The use of Pb(NO3) in an attempt to synthesize a hybrid salt with an L+ cation was not successful but led to the isolation of 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium as a mixed chloride/nitrate salt, [L]2[Cl]1.5[NO3]0.5Á3H2O (II) in the system: 2-PCA – CH3NH2ÁHCl – Pb(NO3)2 – CH3OH The identities of the title compounds were confirmed by elemental analysis, IR and NMR spectroscopy, and singlecrystal diffraction studies.
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