Crystal structure of imidazo[1,5-a]pyridinium-based hybrid salt (C13H12N3)2[MnCl4]

A new organic-inorganic hybrid salt [L]2[MnCl4] (I) where L (+) is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetra-chlorido-manganate(II) anions. The L (+) cation was formed in situ in the oxidative cyclo-condensation of 2-pyridine-carbaldehyde and CH3NH2.HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020 black triangle right) to de-twin the data. The twin law (-1 0 0 0 - 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155 (1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89 (18) and 0.78 (17) degrees ]; the pendant pyridyl rings are twisted by 36.83 (14) and 36.14 (13) degrees with respect to the planes of the remaining atoms of the cations. The tetra-hedral MnCl4 (2-) anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469 (10)-2.3941 (9) A. The distortion value of 0.044 relative to the ideal tetra-hedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak pi-pi stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mncdots, three dots, centeredMn separation in the cation stack is approximately 7.49 A. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting.