Synthesis, Crystal Structure, Fluorescence Properties and Geometrical Calculation of 4,8,10-Trimethyl-2-(3,5-dimethylpyrazol)pyrido-[2',3':3,4]-pyrazol[1,5-a]-pyrimidin

A novel compound 4,8,10-trimethyl-2-(3,5-dimethylpyrazol)-pyrido-2',3':3,4]-pyrazol-1,5-5-a]-pyrimidine (C17H18N6) has been synthesized from 2,6-dichloro-4-methylnico-tinonitrile, hydrazine and acetylacetone by substitution and cyelolization. The structure was characterized by elemental analysis, 1H NMR and IR, and single-crystal structure was determined by X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group P21/c with a = 8.0338(9), b = 28.618(3), c = 7.2688(8) (A),β = 111.051(2)°, V= 1559.6(3) (A)3, Z = 4, Dc=1.305 g/cm3,μ = 0.083 mm-1, Mr = 306.37, F(000) = 648, S = 0.971, the final R = 0.0795 and wR =0.1746 for 1457 observed reflections (Ⅰ > 2σ(Ⅰ)). The results demonstrate that the pyridine, pyrazole and pyrimidine rings are nearly eoplanar, which is evident from the dihedral angles among the four rings in the range of 0.13～4.15°. The face-to-face π-π stacking interactions among pyridine,pyrazol and pyrimidine rings result in a supramolecular crystal, in which they seem to be effective in stabilizing the structure. Meanwhile, the fluorescence properties of the title compound were discussed, which showed very strong fluorescence. The calculated results (selected bond lengths,bond angles and torsion angles) are all typical and agree well with the experimental results, which demonstrates that B3LYP/6-31+G* is suitable for the title compound.