Synthesis, Crystal Structure of a Novel Mn Complex with Nicotinoyl-glycine

A novel manganese complex, C 16 H 26 MnN 4 O 12 , was synthesized by the reaction of nicotinoyl-glycine and NaOH in an ethanol/water solution and structurally characterized by elemental analysis, UV-vis spectrum, IR spectrum and single-crystal X-ray diffraction analysis. The nicotinoyl-glycine ligand acts as a bridging ligand to connect the manganese ions by the hydrogen interactions; thus, the complex expands into a 3D supramolecular net structure.


Introduction
Coordination compounds, a class of newly developed porous inorganic-organic hybrid materials, have attracted much attention, due to their diverse and easily tailored structures [1][2][3][4][5], and their tremendous potential applications in nonlinear optics, catalysis, gas absorption, luminescence, magnetism and so on [6][7][8].To obtain desired coordination compounds, hydrogen bonds, π-π interactions and Van der Waals interactions must be carefully considered [9]; also, the appropriate use of the well-designed multidentate nitrogen ligands and organic carboxylic acid ligands plays an important role in the synthesis of coordination compounds [10].The hydrogen bond is an important element in coordination compounds.The strong and directional nature of hydrogen bonds is exploited in the organized self-assembly of molecules in solution and the solid state.Carboxylic acids and amides are two commonly used functional groups in crystal engineering because they generally form robust architectures via O-H...O and N-H...O hydrogen-bonded dimers [11].
In our experiment, we used nicotinoyl-glycine as a ligand.A manganese ion coordination polymer of this ligand was obtained and characterized by elemental analysis, IR, UV-vis and X-ray single-crystal diffraction analysis.

Elemental Analysis
The result of the elemental analysis showed that the symmetric unit of the Mn(II) coordination polymer is C 16 H 26 MnN 4 O 12 , indicating that the Mn(II) coordination compounds conform to a 1:2 metal-to-ligand stoichiometry.

Structural Description of C 16 H 26 MnN 4 O 12 (1)
The result of the single-crystal X-ray diffraction revealed that complex 1 crystallizes in the triclinic space group P 1 .The asymmetric unit consists of half a Mn(II) ion, one nicotinoyl-glycine ligand and two water molecules.The coordination environment of the manganese center is depicted in Figure 1.As shown in Figure 1, each manganese is octahedrally coordinated by two N atoms(N1, N1 i ) from two nicotinoyl-glycine ligands at the axial positions, and four O atoms(O1w, O1w i , O2w, O2w i ) from four coordination water molecules in the equatorial plane.In complex 1, the nicotinoyl-glycine ligand acts as a bridge to connect two Mn (II) ions by hydrogen-bonding interactions.There are two kinds of element rings in the complex.The two oxygen atoms were linked by hydrogen-bonding interactions (O1w-H1wB...O3, O2w-H2wB...O2), and an element ring was formed.In addition, three oxygen atoms were linked by hydrogen-bonding interactions (O3w-H3wB...O2, O3w-H3wA...O1), and an element ring was formed as well.(Figure 2 shows the two kinds of element rings in the complex.)Furthermore, there are π-π stacking interactions (Figure 3) between the pyridine rings.The complex is extended to a 3D supramolecular net structure by the hydrogen-bond interactions and π-π stacking interactions.The 3D supramolecular net structure is shown in Figure 4.The main bond lengths (Å) and angles ( • ) for 1 are given in Table 1.The details of the hydrogen bond lengths and angles of the complex are given in Table 2.

Structural Description of C16H26MnN4O12 (1)
The result of the single-crystal X-ray diffraction revealed that complex 1 crystallizes in the triclinic space group P1.The asymmetric unit consists of half a Mn(II) ion, one nicotinoyl-glycine ligand and two water molecules.The coordination environment of the manganese center is depicted in Figure 1.As shown in Figure 1, each manganese is octahedrally coordinated by two N atoms(N1, N1 i ) from two nicotinoyl-glycine ligands at the axial positions, and four O atoms(O1w, O1w i , O2w, O2w i ) from four coordination water molecules in the equatorial plane.In complex 1, the nicotinoylglycine ligand acts as a bridge to connect two Mn (II) ions by hydrogen-bonding interactions.There are two kinds of element rings in the complex.The two oxygen atoms were linked by hydrogenbonding interactions (O1w-H1wB…O3, O2w-H2wB…O2), and an element ring was formed.In addition, three oxygen atoms were linked by hydrogen-bonding interactions (O3w-H3wB…O2, O3w-H3wA…O1), and an element ring was formed as well.(Figure 2 shows the two kinds of element rings in the complex.)Furthermore, there are π-π stacking interactions (Figure 3) between the pyridine rings.The complex is extended to a 3D supramolecular net structure by the hydrogen-bond interactions and π-π stacking interactions.The 3D supramolecular net structure is shown in Figure 4.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The details of the hydrogen bond lengths and angles of the complex are given in Table 2.

Structural Description of C16H26MnN4O12 (1)
The result of the single-crystal X-ray diffraction revealed that complex 1 crystallizes in the triclinic space group P1.The asymmetric unit consists of half a Mn(II) ion, one nicotinoyl-glycine ligand and two water molecules.The coordination environment of the manganese center is depicted in Figure 1.As shown in Figure 1, each manganese is octahedrally coordinated by two N atoms(N1, N1 i ) from two nicotinoyl-glycine ligands at the axial positions, and four O atoms(O1w, O1w i , O2w, O2w i ) from four coordination water molecules in the equatorial plane.In complex 1, the nicotinoylglycine ligand acts as a bridge to connect two Mn (II) ions by hydrogen-bonding interactions.There are two kinds of element rings in the complex.The two oxygen atoms were linked by hydrogenbonding interactions (O1w-H1wB…O3, O2w-H2wB…O2), and an element ring was formed.In addition, three oxygen atoms were linked by hydrogen-bonding interactions (O3w-H3wB…O2, O3w-H3wA…O1), and an element ring was formed as well.(Figure 2 shows the two kinds of element rings in the complex.)Furthermore, there are π-π stacking interactions (Figure 3) between the pyridine rings.The complex is extended to a 3D supramolecular net structure by the hydrogen-bond interactions and π-π stacking interactions.The 3D supramolecular net structure is shown in Figure 4.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The details of the hydrogen bond lengths and angles of the complex are given in Table 2.

Structural Description of C16H26MnN4O12 (1)
The result of the single-crystal X-ray diffraction revealed that complex 1 crystallizes in the triclinic space group P1.The asymmetric unit consists of half a Mn(II) ion, one nicotinoyl-glycine ligand and two water molecules.The coordination environment of the manganese center is depicted in Figure 1.As shown in Figure 1, each manganese is octahedrally coordinated by two N atoms(N1, N1 i ) from two nicotinoyl-glycine ligands at the axial positions, and four O atoms(O1w, O1w i , O2w, O2w i ) from four coordination water molecules in the equatorial plane.In complex 1, the nicotinoylglycine ligand acts as a bridge to connect two Mn (II) ions by hydrogen-bonding interactions.There are two kinds of element rings in the complex.The two oxygen atoms were linked by hydrogenbonding interactions (O1w-H1wB…O3, O2w-H2wB…O2), and an element ring was formed.In addition, three oxygen atoms were linked by hydrogen-bonding interactions (O3w-H3wB…O2, O3w-H3wA…O1), and an element ring was formed as well.(Figure 2 shows the two kinds of element rings in the complex.)Furthermore, there are π-π stacking interactions (Figure 3) between the pyridine rings.The complex is extended to a 3D supramolecular net structure by the hydrogen-bond interactions and π-π stacking interactions.The 3D supramolecular net structure is shown in Figure 4.The main bond lengths (Å) and angles (°) for 1 are given in Table 1.The details of the hydrogen bond lengths and angles of the complex are given in Table 2.

UV-Vis Spectrum
Figure 6 shows the UV-vis spectrum of the Mn(II) complex.From Figure 6, we can see the maximum absorption peak of the coordination compound at 201 nm.This indicates that there are large π-conjugated systems in the complex [26].

UV-Vis Spectrum
Figure 6 shows the UV-vis spectrum of the Mn(II) complex.From Figure 6, we can see the maximum absorption peak of the coordination compound at 201 nm.This indicates that there are large π-conjugated systems in the complex [26].

Materials and Instrumentation
Nicotinoyl-glycine ligand, sodium hydroxide (NaOH) and solvents were purchased commercially and used without further purification.The IR spectrum was recorded in the range 4000-400 cm −1 on a Infrared Spectrophotometer (Beijing Purkinje General Instrument, Beijing, China).Elemental analysis for carbon, hydrogen and nitrogen was performed on the Elementar Vario EL III elemental analyzer.UV-Vis spectrum was measured using UV-Visible Spectrophotometer (Beijing Purkinje General Instrument, Beijing, China).Single-crystal data of C16H26MnN4O12 were collected by a Bruker smart CCD diffractometer (Bruker, Billerica, MA, USA).

Data Collection, Structural Determination,and Refinement
A colorless single crystal of the complex 1 with dimensions of 0.20 mm × 0.19 mm × 0.18 mm was selected and mounted on a glass fiber for data collection.The X-ray diffraction data were measured at 293(2) K on a Bruker smart CCD diffractometer with a graphite-monochromatized MoKα (λ = 0.71073 Å) radiation.The structure was solved by direct methods with SHELXL-97 [27] and refined on F 2 by full-matrix least-squares procedures with SHELXTL-97 [27].The non-hydrogen atoms were located refined anisotropically, and hydrogen atoms were added according to theoretical models.The crystal data of 1 are given in Table 3.

Materials and Instrumentation
Nicotinoyl-glycine ligand, sodium hydroxide (NaOH) and solvents were purchased commercially and used without further purification.The IR spectrum was recorded in the range 4000-400 cm −1 on a Infrared Spectrophotometer (Beijing Purkinje General Instrument, Beijing, China).Elemental analysis for carbon, hydrogen and nitrogen was performed on the Elementar Vario EL III elemental analyzer.UV-Vis spectrum was measured using UV-Visible Spectrophotometer (Beijing Purkinje General Instrument, Beijing, China).Single-crystal data of C 16 H 26 MnN 4 O 12 were collected by a Bruker smart CCD diffractometer (Bruker, Billerica, MA, USA).

Data Collection, Structural Determination, and Refinement
A colorless single crystal of the complex 1 with dimensions of 0.20 mm × 0.19 mm × 0.18 mm was selected and mounted on a glass fiber for data collection.The X-ray diffraction data were measured at 293(2) K on a Bruker smart CCD diffractometer with a graphite-monochromatized MoKα (λ = 0.71073 Å) radiation.The structure was solved by direct methods with SHELXL-97 [27] and refined on F 2 by full-matrix least-squares procedures with SHELXTL-97 [27].The non-hydrogen atoms were located refined anisotropically, and hydrogen atoms were added according to theoretical models.The crystal data of 1 are given in Table 3.

Conclusions
In this study, we successfully synthesized and structurally characterized the Mn(II) complex C 16 H 26 MnN 4 O 12 .The structural analyses show that the asymmetric unit of the mononuclear complex consists of half a manganese ion, one nicotinoyl-glycine ligand and two coordinated H 2 O molecules.The nicotinoyl-glycine ligand is a bridging ligand that connects manganese ions by the hydrogen-bond interaction, so the complex expands to a 3D supramolecular net structure.

Figure 1 .
Figure 1.Coordination environment around the Mn(II) ion of complex 1 with labeling scheme at 30% ellipsoidal probability.

Figure 2 .
Figure 2. Two kinds of the element rings in the complex.

Figure 1 .
Figure 1.Coordination environment around the Mn(II) ion of complex 1 with labeling scheme at 30% ellipsoidal probability.

Figure 1 .
Figure 1.Coordination environment around the Mn(II) ion of complex 1 with labeling scheme at 30% ellipsoidal probability.

Figure 2 .
Figure 2. Two kinds of the element rings in the complex.

Figure 2 .
Figure 2. Two kinds of the element rings in the complex.

Figure 1 .
Figure 1.Coordination environment around the Mn(II) ion of complex 1 with labeling scheme at 30% ellipsoidal probability.

Figure 2 .
Figure 2. Two kinds of the element rings in the complex.

Table 3 .
Summary of crystal result for sodium complex.

Table 3 .
Summary of crystal result for sodium complex.