Synthesis, Crystal Structure, and Cytotoxic Activity of a Novel Eight-coordinated Dinuclear Ca(ii)-schiff Base Complex

A novel eight-coordinated dinuclear Ca(II) complex, [Ca 2 (L) 2 (H 2 O) 10 ]·H 2 O (L =

The dinuclear Ca(II) complex are soluble in DMF, DMSO, H 2 O, and CH 3 OH, insoluble in THF, CHCl 3 , and benzene.

IR Spectrum of 1
The IR spectrum of the dinuclear Ca(II) complex is shown in Figure 1.The strong peak at 3473 cm −1 corresponds to the ν(OH) vibration of H 2 O molecules in 1.The peaks at 1683 cm −1 and 1561 cm −1 can be assigned to ν(C=O) and ν(C=N), showing that the C=O and C=N groups do not coordinate to Ca(II) ion [26].The peaks at 1253 cm −1 and 1,192 cm −1 demonstrate the existence of coordination bonds between SO 3 − groups and Ca(II) [27].

IR Spectrum of 1
The IR spectrum of the dinuclear Ca(II) complex is shown in Figure 1.The strong peak at 3473 cm −1 corresponds to the ν(OH) vibration of H2O molecules in 1.The peaks at 1683 cm −1 and 1561 cm −1 can be assigned to ν(C=O) and ν(C=N), showing that the C=O and C=N groups do not coordinate to Ca(II) ion [26].The peaks at 1253 cm −1 and 1,192 cm −1 demonstrate the existence of coordination bonds between SO3 − groups and Ca(II) [27].

1 HNMR and 13 CNMR Spectra of 1
The 1 HNMR and 13 CNMR data of dinuclear Ca(II) complex are as follows: 1
In 1, the two sulfonate groups of each 2.3. 1 HNMR and 13 CNMR Spectra of 1 The 1 HNMR and 13 CNMR data of dinuclear Ca(II) complex are as follows:

Description of 1
The result of X-ray single-crystal diffraction reveals that the novel eight-coordinated dinuclear Ca(II) complex 1 crystallizes in a triclinic P-1 space group.The coordination environment of Ca(II) of 1 is shown in Figure 2. From Figure 2, the asymmetric unit of 1 contains two Ca(II) ions, two 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligands, ten coordinated H 2 O molecules, and one uncoordinated H 2 O molecule.Each Ca(II) ion in 1 is eight-coordinated to three oxygen atoms (O2A, O5, O6 or O2, O5A, O6A) from two 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligands and five coordinated H 2 O molecules (O8, O9, O10, O11, O12 or O8A, O9A, O10A, O11A, O12A).The coordination geometry of Ca(II) can be described as a distorted trigonal dodecahedron.In 1, the two sulfonate groups of each 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligand adopt different coordination modes, one is monodentate and the other is bidentate.The molecules of 1 form a 1D chained structure by the π-π stacking interaction, as shown in Figure 3, and the distance of two planes is 3.428 Å.The 1D chains form a 3D framework structure by the π-π stacking interaction and hydrogen bonds, as shown in Figure 4.The π-π stacking interaction and hydrogen bonds play an important role in stabilizing the 3D framework structure.The main bond lengths (Å) and angles ( • ) for 1 are given in Table 1.The lengths (Å) and angles ( • ) of hydrogen bonds for 1 are listed in Table 2.
Catalysts 2016, 6, 109 3 of 8 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligand adopt different coordination modes, one is monodentate and the other is bidentate.The molecules of 1 form a 1D chained structure by the π-π stacking interaction, as shown in Figure 3, and the distance of two planes is 3.428 Å.The 1D chains form a 3D framework structure by the π-π stacking interaction and hydrogen bonds, as shown in Figure 4.The π-π stacking interaction and hydrogen bonds play an important role in stabilizing the 3D framework structure.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The lengths (Å) and angles (°) of hydrogen bonds for 1 are listed in Table 2.
The Ca-O distances range from 2.3882 (18) to 2.688 (2) Å (Table 1), which are comparable to those in reported Ca(II) complexes [19−25].4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligand adopt different coordination modes, one is monodentate and the other is bidentate.The molecules of 1 form a 1D chained structure by the π-π stacking interaction, as shown in Figure 3, and the distance of two planes is 3.428 Å.The 1D chains form a 3D framework structure by the π-π stacking interaction and hydrogen bonds, as shown in Figure 4.The π-π stacking interaction and hydrogen bonds play an important role in stabilizing the 3D framework structure.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The lengths (Å) and angles (°) of hydrogen bonds for 1 are listed in Table 2.
The Ca-O distances range from 2.3882 (18) to 2.688 (2) Å (Table 1), which are comparable to those in reported Ca(II) complexes [19−25].4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone ligand adopt different coordination modes, one is monodentate and the other is bidentate.The molecules of 1 form a 1D chained structure by the π-π stacking interaction, as shown in Figure 3, and the distance of two planes is 3.428 Å.The 1D chains form a 3D framework structure by the π-π stacking interaction and hydrogen bonds, as shown in Figure 4.The π-π stacking interaction and hydrogen bonds play an important role in stabilizing the 3D framework structure.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The lengths (Å) and angles (°) of hydrogen bonds for 1 are listed in Table 2.

In Vitro Cytotoxic Activity
The data of in vitro cytotoxic activity of dinuclear Ca(II) complex 1 against HL-60 and MLTC-1 are given in Table 3.The concentration of DMSO was controlled under 1% to assure not to affect the results.The results show that the dinuclear Ca(II) complex 1 has an obvious cytotoxic effect against HL-60 cells and MLTC-1 cells.The dinuclear Ca(II) complex 1 has a stronger cytotoxicity against MLTC-1 cells with lower IC50 (19.51 µg/mL).

Materials and Instrumentation
3-Pyridinecarboxylic hydrazide, disodium 4-formylbenzene-1,3-disulfonate, Ca(ClO 4 ) 2 •4H 2 O, and solvents were obtained from commercial sources and used without further purification.Elemental analysis was carried out on an Elementar Vario EL III analyzer (Elementar, Hanau, Germany).The IR spectrum was recorded in the 4000-400 cm −1 range on an infrared spectrophotometer (Beijing Purkinje General Instrument, Beijing, China). 1 H NMR and 13 CNMR spectra were recorded on a Bruker Avance-400 spectrometer with DMSO-d 6 as the solvent.Crystal data of the dinuclear Ca(II) complex 1 were collected by a Bruker Smart CCD diffractometer (Bruker, Billerica, MA, USA).

Crystal Structure Determination
A single crystal of dinuclear Ca(II) complex 1 with dimensions of 0.22 mm × 0.21 mm × 0.20 mm was chosen for data collection.The X-ray diffraction data of dinuclear Ca(II) complex 1 were collected on a Bruker Smart CCD diffractometer with a graphite-monochromatized MoKα (λ = 0.71073 Å) radiation using the ω-ϕ scan mode (1.66 • ≤ θ ≤ 25.09 • ).The structure was solved by direct methods with SHELXL-97 [28] and refined on F 2 by full-matrix least-squares procedures with SHELXTL-97 [29].The crystal data of 1 are given in Table 4.

Table 3 .
In vitro cytotoxic activities of 1.

Table 4 .
Crystal data for complex 1.