The Synthesis and Crystal Structure of Two New Hydrazone Compounds

Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1) and 2-nitrobenzaldehyde-2-furan formylhydrazone (2), were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = 7.0321(14) Å, b = 7.3723(15) Å, c = 13.008(3) Å, α = 98.66(3) ̋, β = 101.69(3) ̋, γ = 92.25(3) ̋, V = 651.2(2) Å3, Z = 2, Dc = 1.358 g ̈ cm ́3, μ = 0.106 mm ́1, F(000) = 280, and final R1 = 0.0564, wR2 = 0.1420. Compound 2 crystallizes in monoclinic, space group P21/c with a = 17.3618(9) Å, b = 9.1506(4) Å, c = 15.5801(7) Å, β = 104.532(5) ̋, V = 2396.05(19) Å3, Z = 8, Dc = 1.437 g ̈ cm ́3, μ = 0.111 mm ́1, F(000) = 1072, and final R1 = 0.0633, wR2 = 0.1649. Compound 1 forms a 2D-layered structure via the interactions of 1D chains and Compound 2 forms a 3D network structure via the interactions of 1D chains.


Introduction
Hydrazone compounds (-NH-N=C-) and their complexes have been widely studied due to their facile synthesis and potential biological activities [1][2][3][4][5].During recent years, many hydrazone compounds and their complexes have displayed novel structures and extensive applications in luminescent probes, antibacterial and antitumor agents, fluorescence markers, optical materials, and anticonvulsant agent [6][7][8][9][10][11].In the past ten years, we have done some work in the synthesis, structural characterization, and properties of hydrazone compounds, which show novel structures and luminescent properties [12][13][14][15][16].In this paper, two new hydrazone compounds have been synthesized via the classical synthesis method, and their crystal structures have also been determined by X-ray single crystal diffraction analysis.The schemes of the compounds are given in Figure 1.

Introduction
Hydrazone compounds (-NH-N=C-) and their complexes have been widely studied due to their facile synthesis and potential biological activities [1][2][3][4][5].During recent years, many hydrazone compounds and their complexes have displayed novel structures and extensive applications in luminescent probes, antibacterial and antitumor agents, fluorescence markers, optical materials, and anticonvulsant agent [6][7][8][9][10][11].In the past ten years, we have done some work in the synthesis, structural characterization, and properties of hydrazone compounds, which show novel structures and luminescent properties [12][13][14][15][16].In this paper, two new hydrazone compounds have been synthesized via the classical synthesis method, and their crystal structures have also been determined by X-ray single crystal diffraction analysis.The schemes of the compounds are given in Figure 1.

Description of Compounds 1 and 2
The molecular plots of Compounds 1 and 2 with the atomic labeling scheme are given in Figure 2. Compound 1 is of an almost coplanar configuration with a dihedral angle of 2.5 ˝between Plane 1 (C9-N3-C10-N4-C11) and Plane 2 (C1-C2-C3-C4-C5-C6).The crystal structure analysis shows that Compound 1 contains two lattice water molecules.From the bond length data, it can be seen that the C8-N2 bond length of 1.2760 (17) Å is shorter than that of C7-N1 (1.3464(16) Å), which indicates that the bond of C8-N2 is a double bond.Moreover, the C7-O2 bond length of 1.226(2) Å is shorter than that of C3-O1 (1.3537(16) Å), which indicates that the bond of C7-O2 is also double bond.The molecules of both Compound 1 and Compound 2 form a 1D-chained structure via the intermolecular hydrogen bonds (N-H...O) (Figure 3).In addition, Compound 1 forms a two-dimensional layered structure via the interactions of 1D chains (Figure 4).Furthermore, Compound 2 forms a three-dimensional network structure via the interactions of 1D chains (Figure 4).The bond lengths and bond angles in Compounds 1 and 2 are in accordance with the results in [17,18].

4-formylimidazole,
2-nitrobenzaldehyde, 4-hydroxybenzhydrazine, and 2-furan formylhydrazine were purchased from the Xiya Reagent Company.The analyses of C, H, and N were made on an Elementar Vario EL III elemental analyzer (Elementar, Hanau, Germany).IR spectra were recorded as KBr pellets with a Nicolet AVATAR 360 FTIR spectrometer (Nicolet Instrument Inc., Madison, WI, USA) in the 4000~400 cm −1 region. 1 H NMR spectra were recorded on a Bruker Avance-400 spectrometer (Bruker, Elisabethhof, Netherlands) with C2D6OS as the solvent.The X-ray single-crystal data collection for the hydrazone compounds 1 and 2 were performed on a Bruker Smart-1000 CCD diffractometer (Bruker, Billerica, MA, USA).

Materials and Instrumentation
4-formylimidazole, 2-nitrobenzaldehyde, 4-hydroxybenzhydrazine, and 2-furan formylhydrazine were purchased from the Xiya Reagent Company.The analyses of C, H, and N were made on an Elementar Vario EL III elemental analyzer (Elementar, Hanau, Germany).IR spectra were recorded as KBr pellets with a Nicolet AVATAR 360 FTIR spectrometer (Nicolet Instrument Inc., Madison, WI, USA) in the 4000~400 cm ´1 region. 1 H NMR spectra were recorded on a Bruker Avance-400 spectrometer (Bruker, Elisabethhof, Netherlands) with C 2 D 6 OS as the solvent.The X-ray single-crystal data collection for the hydrazone compounds 1 and 2 were performed on a Bruker Smart-1000 CCD diffractometer (Bruker, Billerica, MA, USA).

Crystal Structure Determination
The important crystal data of Compound 1 and Compound 2 are listed in Table 1.Diffraction data of both Compound 1 and Compound 2 were collected at 293 (2) K on a Bruker Smart-1000 CCD diffractometer by using a φ~ω scan mode.The structures were solved via direct methods with SHELXL-97 program package [19] and refined with SHELXTL-97 [20].

Table 1 .
Crystal data for 1 and 2.