Syntheses, Crystal Structures and Properties of Mn(II) and Co(II) Coordination Complexes Based on 1,10-Phenanthroline Derivative①

ZHANG Hua JI Liu-Qing SONG Yu-Zhu KONG Zhi-Guo LI Cong WANG Xiu-Yan

Syntheses, Crystal Structures and Properties of Mn(II) and Co(II) Coordination Complexes Based on 1,10-Phenanthroline Derivative①

ZHANG Huaa, b, cJI Liu-QingcSONG Yu-ZhucKONG Zhi-Guoa, b, cLI Conga, b, cWANG Xiu-Yana, b, c②

a(130103)b(130103)c(136000)

Two new coordination complexes [Mn(L)2(DNSA)] (1) and [Co(L)(1,4-bdc)]n(2)have been achieved under hydrothermal conditions (H2DNSA = 3,5-dinitro-salicylic acid, 1,4-bdc = 1,4-benzenedicarboxylic acid and L = 2-(2-fluoro-6-fluorophenyl)-1-imidazo[4,5-][1,10]phenanthroline).1 crystallizes in monoclinic, space group21/with= 15.871(3),= 17.274(4),= 16.078(3) Å,= 113.03(3)o,= 4056.6(16) Å3,= 4, C45H22Cl2F2MnN10O7,M= 978.57,D= 1.602 g/cm3,(000) = 1980,(Mo) = 0.536 mm–1,= 0.0437 and= 0.1065.2 belongs to the monoclinic system, space group2/with= 14.665(2),= 30.856(4),= 11.237(2) Å,= 111.166(2)o,= 4742.0(12) Å3,= 8, C27H14ClCoFN4O4,M= 517.80,D= 1.602 g/cm3,(000) = 2312,(Mo) = 0.889 mm–1,= 0.0364 and= 0.0862.The central Mn(II) ion in 1 is six-coordinatedby four nitrogen atoms from two L ligands and two oxygen atoms from one DNSA anion.In 2, the two kinds of 1,4-bdc ligands link neighboring Co(II) atoms to yield a two-dimensional layer structure.The luminescence of 1 has been studied in detail.Moreover, thermal behaviors of 1 and 2 are also investigated.

crystal structure, coordination complex,1,10-phenanthroline derivative, thermal behavior;

1 INTRODUCTION

Recently, the design and synthesis of new coordination complexes are currently attracting considerable attention due to their potential applications as functional materials[1-4].It is well known that novel complexes can be specially designed under hydrothermal conditions by the selection of metal ions with preferred coordination geometries, in consideration of the structures of organic ligands and the effects of reaction conditions[5-7].Therefore, great quantities of coordination complexes with fascinating topological structures and properties have been synthesized and reported so far[8-11].As we know, covalent bonds and noncovalent intermolecular forces can be used to construct various supramolecular architectures[12].Recent study indicates that 1,10-phenanthro- line derivatives have been widely used to construct supramolecular architectures not only because of their excellent coordinating ability, but also of their large conjugated system and good accepter-donor system to form-interactions and hydrogen bonding interactions.Based on those factors, a number of coordination complexes have been prepared from zero-dimensional molecules or one-dimen- sional chains, generating extended two-dimensional layers or three-dimensional network supramolecular structures through-interactions and hydrogen bonding interactions[13, 14].So, we selected 1,10-phenanthroline derivative, 2-(2-fluoro-6- fluorophenyl)-1-imidazo[4,5-][1,10]phenanthroline (L), as a N-donor chelating ligand and two carboxylate ligands as organic linkers, yielding two coordination complexes, namely [Mn(L)2(DNSA)] (1) and [Co(L)(1,4-bdc)]n(2).

2 EXPERIMENTAL

2.1 Generals

The commercially available reagents were used without further purification.Elemental analysis was measured on a Perkin-Elmer 240 CHN elemental analyzer.The powder X-ray diffractions (PXRD) were measured on a Rigaku Dmax 2000 X-ray diffractometer with graphite-monochro- matized Curadiation.The emission spectra were measured on a Renishaw inVia Raman Microscope.Thermal stability experiment was performed on a TG SDT2960 thermal analyzer under a nitrogen atmosphere.

2.2 Synthesis of [Mn(L)2(DNSA)] (1)

A mixture of H2DNSA (0.30 mmol), MnSO4(0.30 mmol) and L (0.25 mmol) was dissolved in 12 mL water.When the pH value of the mixture was adjusted to ca.7.5 with KOH, the solution was put into a 25-mL Teflon-lined Parr and heated in an autoclave at 150 °C for 4 days, obtaining yellow crystals of 1 in 31% yield based on L.Anal.Calcd.for C45H22Cl2F2MnN10O7(%): C, 55.23; H, 2.27; N, 14.31.Found (%): C, 55.09; H, 2.23; N, 14.19.

2.3 Synthesis of [Co(L)(1,4-bdc)]n (2)

The pH value of a mixture of 1,4-H2bdc (0.30 mmol), Co(NO3)2∙6H2O (0.10 mmol) and L (0.05 mmol) in 10 mL water distilled water was adjusted to 5.7 with KOH.The resultant solution was heated at 185 °C in a 25-mL Teflon-lined stainless-steel autoclave for 4 days, resulting in brown crystals of 2 with the yield of 42% based on L.Anal.Calcd.for C27H14ClCoFN4O4(%): C, 56.71; H, 2.47; N, 9.80.Found (%): C, 56.43; H, 2.41; N, 9.72.

2.4 X-ray structure determination

A crystal of 1 suitable for X-ray diffraction was chosen and mounted on a Bruker P4 diffractometer equipped with graphite-monochromatized Mo(= 0.71073 Å) radiation by using anscan method at 293(2) K.And a crystal of 2 was selected for data collection performed on a Rigaku RAXIS-RAPID CCD detector diffractometer equipped with graphite-monochromatic Moradiation (= 0.71073 Å) with anscan mode at 293(2) K.The crystal structures were solved by direct methods with SIR2014 (Burla et al., 2014)[15]and refined with SHELXL2018/3 (Sheldrick, 2015)[16]by full-matrix least-squares techniques on2.The non-hydrogen atoms of the complexwere refined with anisotropic temperature parameters.All H atoms were positioned geometrically (C–H = 0.93 Å) and refined as riding withiso(H) = 1.2eq(carrier).

3 RESULTS AND DISCUSSION

3.1 Description of the crystal structure

Selected bond lengths and bond angles of 1 and 2 are given in Table 1, and hydrogen bond lengths and bond angles of 1 in Table 2.The asymmetric unit of 1 consists of one Mn(II) atom, two L ligands and one DNSA anion (Fig.1).Each Mn(II) atom is six-coordinated by two oxygen atoms (O(1) and O(2)) from one DNSA anion, and four nitrogen atoms (N(1), N(2), N(5) and N(6) are from two L ligands in a distorted octahedral coordination sphere.The atoms N(1), N(2), N(5) and O(1) constitute the basal plane of the octahedron, while N(6) and O(2) are located at the axial positions.The Mn–O bond lengths range from 2.100(2) to 2.118(2) Å, and the Mn–N distances vary from 2.256(2) to 2.303(2) Å.The carboxylate group of DNSA anion shows a1:0monodentate mode, whereas each DNSA anion chelates one Mn(II) atom in a bidentate mode.The adjacent [Mn(L)2(DNSA)] moleculesform a bimolecular structure through NH∙∙∙O (N(3)H(3A)∙∙∙O(2)ii, N(3)H(3A)∙∙∙O(3)ii, symmetric code:ii1,,1, as shown in Table 2) hydrogen-bonding interactions(Fig.2).Furthermore, the bimolecular structures are linked into a two-dimensional supramolecular layer structure by NH∙∙∙N (N(7)H(7A)∙∙∙N(4)v, symmetric code:v1/2, –+1/2,+1/2, as illustrated in Table 2) hydrogen-bonding interactionsbetween the adjacent bimolecular structures (Fig.2).

Table 1.Selected Bond Lengths (Å) and Bond Angles (°) for 1 and 2

Symmetry transformationused to generate the equivalent atoms:2(i) –x + 1, y, –z + 1/2;(ii) –x, –y + 1, –z + 1;(iii)–x,y,–z + 1/2

Table 2.Hydrogen Bond Lengths (Å) and Bond Angles (°) for 1

Symmetry transformation:1(i)– 1/2, –+ 1/2,– 1/2; (ii) –+ 1, –, –+ 1;(iii)–1/2,– 1/2,–3/2; (iv)–1/2,1/2, –1/2; (v)– 1/2,–1/2,1/2

Fig.1.View of the molecular structure of 1

Fig.2.View of the layer structure of 1 formed by hydrogen-bonding interactions (N–HO and N–HN)

As can be observed in Fig.3, there are one Co(II) atom, one L ligand, and two halves of 1,4-bdc anions in the asymmetric unit of 2.The 1,4-bdc anion resides on an inversion center.Each Co(II) atom is six-coordinated by two nitrogen atoms from one L ligand (Co(1)N(1) = 2.134(2), Co(1)N(2) = 2.147(2) Å), and four carboxylate oxygen atoms from three different 1,4-bdc anions(Co(1)O(1) = 2.362(2), Co(1)O(2)= 2.1231(18) Å, Co(1)O(3) = 2.0481(18), Co(1)O(4)iii= 2.0304(18) Å, symmetric code:iii–,, –+1/2).In particular, the two 1,4-bdc anions show different coordination modes (Fig.3).For convenience,the 1,4-bdc anions containing the oxygen atoms labeled O(1) and O(3) are designated 1,4-bdc1 and 1,4-bdc2, respectively.Each carboxylate groupof1,4-bdc2 bridges two Co(II) atoms in a bis-bridging mode, whereas each carboxylate group of 1,4-bdc1 anion chelates one Co(II) atom in a bis-chelating mode to yield a dimer.The distance between the Co(II) atoms in the dimer is about 10.879 Å.Most interestingly, the binuclear units are bridged by the backbones of 1,4-bdc2 ligands to form a chain structure (Fig.4) and are further connected by the 1,4-bdc2 ligands in bis-chelating modes to give rise to a layer structure (Fig.4).The L ligands are attached to both sides of the layer structures, which allow the formation ofstacking between the two pyridine rings of the L ligands with the centroid-to-centroid distance of 3.764(2) Å and face-to-face distance of 3.387(1) Å, and the dihedral angle between the two planes is0.0(1)o(Two pyridine rings are composed of N(1)/C(1)～C(5) and N(1)iv/C(1)iv～C(5)iv, respectively; symmetry code:iv–1/2, –1/2, –+ 1) (Fig.6).Thesestacking interactions linked the adjacent layers into a 3D supramolecular architecture (Fig.4).

Fig.3.Coordination environmentof 2 (Symmetric codes: (i) –1,, –1/2; (ii) –, –1, –1;(iii)–,,–1/2)

Fig.4.Three-dimensional supramolecular architecture of the title complex constructed byinteractions

3.2 PXRD patterns and UV-vis absorption spectrum

The powder X-ray diffraction (PXRD) patterns for complexes 1 and 2 were recorded at room temperature to confirm their phase purity (Fig.5).The experimental PXRD patterns of 1 and 2 well correspond to the simulated ones of 1 and 2, respectively, indicating the synthesized bulk materials and the measured single crystals are the same.The UV-vis absorption spectra of 1 were registered from the crystalline state at r.t.(Fig.6).The energy bands of 1 from 200 to 560 nm can be assigned as metal-to-ligand charge-transfer (MLCT) transitions[17].The above analysis is consistent with the crystal structure determination.

Fig.5.Experimental and simulated PXRD patterns of 1 and 2

Fig.6.UV-vis absorption spectrum of 1

3.3 Luminescent properties

The luminescent properties of the free organic ligands and complex 1 have been studied in the solid state at room temperature (Fig.7).The main emission peaks of H2DNSA and L are located at about 548 (ex= 325 nm) and 404 nm (ex= 325 nm), respectively,which may be attributed toor* →transition[18].Complex 1 shows an emission band at 545 nm (ex= 325 nm).This emission is similar to that of H2DNSA (em= 545 nm).Therefore, the emission of 1 should originate from the H2DNSA ligand.

3.4 Thermogravimetric analysis

The stabilities of 1 and 2 were evaluated by thermo- gravimetric analysis (TGA).As depicted in Fig.8,the TGA curve of 1 shows two main steps of weight loss.The first step of 21.4% from 202 to 310 °C corresponds to the release of the organic group C7H2N2O6of DNSA anions (calcd.21.5%), and the second step of 71.2% in the range of 317～572 °C to the elimination of L ligands (calcd.: 71.3%).The anhydrous complex 2 begins to decompose at 227 °C and ends above 632 °C.The weight loss is attributed to both L ligands and the organic group C8H4O3of 1,4-bdc anions (obsd.86.8%, calcd.86.9%).However, it is difficult to determine this weight loss accurately as these processes are overlapped with the weight loss due to the dissociation of organic fractions.

Fig.7.Solid state emission spectra of 1,2,3-H2DNSA, L and 1 at room temperature

Fig.8.TGA curves of complexes 1 and 2

4 CONCLUSION

Two new coordination complexes, [Mn(L)2(DNSA)] (1) and [Co(L)(1,4-bdc)]n(2), have been successfully synthesi- zed by the reaction of two transition metal ions, different aromatic carboxylic ligands and 2-(2-fluoro-6-fluorophenyl)- 1H-imidazo[4,5-f][1,10]phenanthroline (L) with different architectures under hydrothermal conditions.The difference of the structures indicates that carboxylic ligands and metal cations play important roles in the formation of complexes.1 shows weak emission in the solid state at room temperature.The thermal behaviors of 1 and 2 have been studied.We believe that more metal complexes containing L ligand with interesting structures and physical properties will be synthesized in the future.

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10 June 2020;

7 August 2020 (CCDC 2017284 and 2017285)

the National Natural Science Foundation of China (No.21805110)

.Majoring in coordination chemistry.E-mail: wangxiuyanjlnu2004@163.com

10.14102/j.cnki.0254–5861.2011–2901