The crystal structure of 1,4-bis(1 H -imidazol- 3-ium-1-yl)benzene dinitrate, C 12 H 12 N 4 2

[H 2 (C 12 H 10 N 4 )] 2 + ·2(NO 3 ) − , monoclinic, P 2 1 / c (no. 14), a = 3.6937(3) Å, b = 15.5641(10) Å, c = 12.3322(8) Å, β = 93.201(7) ° , V = 707.86(9) Å 3 , Z = 2, R gt ( F ) = 0.0377, wR ref ( F 2 ) = 0.1076, T = 298.15 K.


Comment
The choice and design of organic ligands are of great importance in the construction of MOFs.7][8] Three crucial points should be considered in choosing ligands: (i) The coordination ability between ligands and transition metal (TM) ions.Initially, pyridine-based bridging ligands were widely used in the construction of POM-based networks.0][11] (ii) The rigidity and flexibility of the ligands.3][14][15] (iii) The length of bridging ligands should be similar to the diameter of the Keggin-type anions.If the organic ligand is too short, the pores of the metal-organic frameworks will be occupied or terminated by POM anions, making it harder to generate frameworks. 16Using 1,4-bis-(1H-imidazol-1-yl)benzene as the structural model for retrieval, there were found 570 crystal structure hits in the Cambridge Crystal Structural Database (ConQuest 2022.3.0,CSD), in which there are a total of 42 crystal structures containing 1,4-bis(1H-imidazol-3-ium-1-yl)benzene.8][19] To the best of our ability, only 2 crystal structures with 1,4-bis(1H-imidazol-3-ium-1-yl)benzene crystallization in inorganic anion with balanced charge, were searched in the CSD, i.e. 1,4-bis(1H-imidazol-3-ium-1-yl)benzene diperchlorate 20 and 1,1′-(p-phenylene)-bis(1H-imidazol-3-ium) hexafluorosilicate(iv). 21More importantly, 1,4-bis-(1Himidazol-1-yl)benzene and its derivatives have been found to possess widespread biological activities, many of them have been developed as medical and functional materials.Based on the above considerations, the title compound, (I), (Figure 1) was obtained unexpectedly as the product of an attempted synthesis of a network complex of Zn(II) using mixed H 2 O/anhydrous ethanol/DMF as the solvent.
In the crystal of (I), all potential hydrogen bond acceptors and donors participate in charge-assisted hydrogen bonding interactions.Interestingly, the cations and anions associate about a 2-fold axis via imidazole-N-H⋯O (nitrate) ⋯H-N-imidazole hydrogen bonds leading to three edgesharing hydrogen-bonded rings, i.e. a four-membered R 4 The dihedral angles between the Cg2/Cg2 vi or Cg2/Cg2 vii or Cg2/Cg2 viii or Cg2/Cg2 ix is 0.00°, with a centroid-to-centroid distance of 3.6937(10) Å, and a perpendicular distance of 3.4207(15) or 3.4580(13) Å.It is worth mentioning that the two Cg⋯Cg distances and their dihedral angles are almost the same.However, their contribution to the overall lattice energy must be very small.Thus a supramolecular 3D network fragment is formed by N-H⋯O, C-H⋯O, and π⋯π interactions stabilizing the compound.Furthermore, PLATON 5 analysis shows that the unit cell contains no residual solvent accessible void.

Figure 1 :
Figure 1: The one-dimensional hydrogen bonding chain formed between the cations [H 2 bib] 2+ and the anions [NO 3 − ], and further assembled to a two-dimensional layer structure with the π⋯π interactions in I. (a) The one-dimensional hydrogen bonding (N-H⋯O hydrogen bonds as green dashed lines) structure of I, showing the part atom numbering scheme (symmetry codes: i 1-x, 1−y, 2−z<; ii 2−x, 1−y, 1-z); (b) View of the 2D π⋯π interactions and N-H⋯O hydrogen bonded framework in I.The π⋯π interactions and N-H⋯O hydrogen bonds show as dashed lines.

Table  :
Data collection and handling.

Table  :
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å  ).