Three Nickel/maleonitriledithiolate Complexes Accompanied by Different Organic Molecules: Syntheses, Crystal Structures and Properties①

YAN Wei-HongSHEN Ming-Le JI E-Yu HUANG Ya-Ping LIU Xue-Guo

(Nanyang Key Laboratory of Industrial Microbiology, School of Biology and Chemical Engineering, Nanyang Institute of Technology, Nanyang 473004, China)

Three Nickel/maleonitriledithiolate Complexes Accompanied by Different Organic Molecules: Syntheses, Crystal Structures and Properties①

YAN Wei-Hong②SHEN Ming-Le JI E-Yu HUANG Ya-Ping LIU Xue-Guo

(Nanyang Key Laboratory of Industrial Microbiology, School of Biology and Chemical Engineering, Nanyang Institute of Technology, Nanyang 473004, China)

Three complexes [AMP][Ni(mnt)2]·CH3CN (1, AMP = 1-(9-anthrylmethyl)pyridinium), [DPI]2[Ni(mnt)2]I (2, DPI = diphenyliodonium) and [DD][Ni(mnt)2]2·2H2O (3, DD = dimethylenediamine) have been prepared and characterized by elemental analyses and IR spectroscopy.X-ray diffraction studies show that three complexes crystallize in the same triclinic space group P1, and anionic accumulations are formed in a column shape.The results show that different counter-cations could induce versatile anionic stacks.The structures of three complexes exhibit rich hydrogen bonding interactions.In addition, UV-VIS properties of them are also investigated .

maleonitriledithiolate, syntheses, crystal structure;

1 INTRODUCTION

Weak interactions play an important role in many fields such as chemistry, physics and biology, and researches on them have been developed rapidly.During the development of supramolecular chemistry, weak interactions have been of great interest, such as H-bonding, p··p stacking interactions, etc[1-6].It is well known that the selection of ligands is important for the construction of supramolecular structures.In the past few decades, considerable interest has been focused on maleonitriledithiolate complexes because of their special structures and great potential in diversified applications, such as conducting, magnetic materials, dyes, non-linear optics[7-10], and so on.Herein, we select maleonitriledithiolate (mnt2-) as the ligand.The ligand possesses planar conjugate structures and contains N & S atoms, so it is easy to form accumulation of hydrogen bonds.As can be seen from the previous reports[11-14], different counter-cations could induce versatile anion stack modes and bis(maleonitriledithiolate) complexes exhibit various weak interactions and diversity magnetic changes[15-21].Especially in 2011, Prof.Ren’s Group studied magnetic phase transition properties of the Spin-Peierls-type molecule-based magnets via tuning the isotopic substitutions[22].The work again inspires researchers to pay more attention to the classical ligand.As an extension of the study based on the mnt2-ligand, we chose two monovalent cations [AMP]+, [DPI]+and one bivalent cation [DD]2+as counter-cations in this paper.Three complexes of [AMP][Ni(mnt)2]·CH3CN (1), [DPI]2[Ni(mnt)2]I (2)and [DD][Ni(mnt)2]2·2H2O (3) have been synthesized.Their crystal structures and UV-VIS properties have been investigated.

2 EXPERIMENTAL

2.1 Reagents and instruments

All reagents and solvents were purchased from commercial sources and used without further purification.Na2mnt and 1-(9-anthrylmethyl)pyridinium chloride ([AMP]Cl) were prepared according to the literature[23,24].Elemental analyses were performed on a PE-240C elemental analyzer.The infrared spectra were recorded on a VECTOR 22 spectrometer with pressed KBr pellets in the range of 4000～400 cm-1.The UV-VIS spectrum was recorded on a Perkin-Elmer Lambda 950 UV/VIS spectrometer.

2.2 Synthesis of complex [AMP][Ni(mnt)2]·CH3CN (1)

Na2mnt (0.074 g, 0.4 mmol), NiCl2·6H2O (0.048 g, 0.2 mmol) and [AMP]Cl (307.09) (0.06 g, 0.2 mmol) were dissolved into 25 mL H2O.Then I2(0.059 g, 0.25 mmol) was added into the solution.The mixture was stirred at room temperature for 24 h, to oxide Ni2+ion to Ni3+ion by iodine.A black precipitate given was filtered off, washed by water and dried under vacuum.The precipitate was dissolved in MeCN and the obtained solution was left to evaporate at room temperature.One week later, black crystals were obtained with 11% yield based on nickel.Anal.Calcd.for C30H19N6NiS4(%): C, 55.39; H, 2.94; N, 12.92.Found (%): C, 55.41; H, 2.91; N, 12.95.IR (KBr, cm-1): 3448(m), 2207(s), 1627(m), 1477(m), 1255(w), 1158(m), 735(m), 676(w), 506(w).

2.3 Synthesis of complex [DPI]2[Ni(mnt)2]I (2)

Complex 2 was obtained by the same procedure used for the preparation of 1 except that [AMP]Cl was used instead of C12H10F6IP as a starting material.Six days later, black crystals were obtained with 10% yield based on nickel.Anal.Calcd.for C32H20I3N4NiS4(%): C, 37.38; H, 1.96; N, 5.45.Found (%): C, 37.31; H, 1.89; N, 5.48.IR (KBr, cm-1): 3448(s), 2202(s), 1633(s), 1486(m), 1153(m), 748(w), 674(m), 622(w).

2.4 Synthesis of complex [DD][Ni(mnt)2]2·2H2O (3)

Na2mnt (0.074 g, 0.4 mmol), NiCl2·6H2O (0.048 g, 0.2 mmol) and [(CH2)2(NH2)2](HCl)2(0.013 g, 0.1 mmol) were dissolved into 25 mL H2O.Then I2(0.059 g, 0.25 mmol) was added into the solution.The mixture was stirred at room temperature for 24 h, to oxide Ni2+ion to Ni3+ion by iodine.A black precipitate given was filtered off, washed by water and dried under vacuum.The precipitate was dissolved in MeCN and the obtained solution was left to evaporate at room temperature.One week later, black crystals were obtained with 9% yield based on nickel.Anal.Calcd.for C9H7N5OS4Ni (%): C, 27.85; H, 1.82; N, 18.04.Found (%): C, 27.81; H, 1.87; N, 18.01.IR (KBr, cm-1): 3635(m), 3449(m), 2200(s), 1639(m), 1493(m), 1323(w), 1154(w), 1026(w), 804(w), 566(w).

2.5 Structure determination and refinement

Suitable single crystals of three complexes were mounted on a Bruker Smart Apex CCD diffractometer with graphite-monochromated MoKa radiation with l = 0.71073 ?.A hemisphere of the data was collected at room temperature for complexes 1, 2 and 3 at 130 K.The numbers of observed and unique reflections are 10474 and 5485 (Rint= 0.0255) for 1, 10736 and 6783 (Rint= 0.0130) for 2 and 6678 and 2354 (Rint= 0.0429) for 3.The data were integrated using the Siemens SAINT program[25].The structures were solved by direct methods and refined by full-matrix least-squares against F2using the SHELXTL crystallographic software package[26].All non-hydrogen atoms were refined anisotropically.Complex 1 is of triclinic system, space group P1 with a = 8.519(7), b = 13.216(11), c = 14.393(13) ?,a = 113.525(14), β = 91.565(16), γ = 93.182(15)o, V = 1481(2) ?3, Z = 2, S = 0.985, Ra= 0.0357 and wRb= 0.0936 (I > 2σ(I)).Complex 2 adopts triclinic space group P1 with a = 9.5635(8), b = 12.8502(11), c = 15.4793(13) ?, a = 104.9220(10), β =92.2990(10), γ = 94.1230(10)o, V = 1830.0(3) ?3, Z = 2, S = 1.035, Ra= 0.0223 and wRb= 0.0506 (I > 2σ(I)).Complex 3 is triclinic, space group P1 with a = 6.474(3), b = 7.336(3), c = 14.851(6) ?, a = 96.644(7), β = 92.038(7), γ = 99.182(7)o, V = 690.5(5) ?3, Z = 2, S = 1.008, Ra= 0.0434 and wRb= 0.1068 (I > 2σ(I)).aR = S|Fo| - |Fc|/S|Fo|,bwR =lengths and bond angles are given in Table 1, and the selected hydrogen bond distances and bond angles in Table 2.

Table 1.Selected Bond Lengths (?) and Bond Angles (°) for Complexes 1～3

Table 2.Hydrogen Bond Lengths (?) and Bond Angles (°) for Complexes 1～3

3 RESULTS AND DISCUSSION

3.1 Crystal structural description

Complex 1 crystallizes in the triclinic space group P1.An ORTEP drawing of 1 is shown in Fig.1.Each Ni(III) ion is coordinated by four sulfur atoms, and exhibits square-planar coordination geometry.The Ni–S distances as well as the S–Ni–S angle are normal, which are comparable to those in the reportedcomplexes[27-29].Within an anion stack, the Ni(III) ions form a chain with Ni··Ni distances being 8.519 ?.The distance ofadjacent Ni(III) ions is too long to be considered as the Ni··Ni interaction (Fig.2a).The other interactions are found among cations, anions and acetonitrile molecules.C(14)··N(4A), C(11B)··N(2A) and C(27B)··N(2) in the cations and anions had hydrogen bonding interactions based on its distances of 3.251, 3.558 and 3.389 ?, respectively[30].While the cations and acetonitrile molecules also exhibit hydrogen bonds C(14B)··N(6B) with distance to be 3.498 ? (Symmetry codes: A = 1+x, y, z; B = x, y, 1+z) (Fig.2b).Extensive hydrogen-bonding interactions here contributed to a segregated column structure of cations and anions, which is a three-dimensional supramolecular structure, as demonstrated in Fig.2c.

Fig.1.Coordination environment of complex 1.The hydrogen atoms are omitted for clarity

Fig.2.(a) Side view of the anions stacking of complex 1.(b) Hydrogen bonding interactions between the cations, anions and solvent molecules.(c) Packing diagram for complex 1.Symmetry codes: A = 1+x, y, z; B = x, y, 1+z

The crystal of 2 belongs to a triclinic system with space group P1.All Ni-S bond lengths and S-Ni-S bond angles fall within normal ranges (Fig.3).Within an anion stack, the Ni(III) ions form a chain with the Ni··Ni distances being 9.564 ? (Fig.4a).The weak interactions are also observed in complex 2, which is C(27A)··N(1) with the distance of 3.381 ? (Symmetry code: A = -1+x, y, z).In addition, there is another C-H··p weak interaction between C(29) and the benzene rings center with the distance of 2.884 ?, as shown in Fig.4b.Complex 2 also shows segregated column stacks of cations and anions (Fig.4c).

X-ray crystallography analysis reveals that complex 3 crystallizes in triclinic space group P1, and coordination environment of 3 is shown in Fig.5.The Ni(III) ion in each [Ni(mnt)2]-is coordinated by four sulfur atoms of two mnt2-, and exhibitsquasi-square planar coordination geometry.The average distance of Ni(1)-S is 2.152 ? and the average angle of S-Ni(1)-S is 90.00o, which are comparable to the reported values for [Ni(mnt)2]-complexes.

Fig.3.Coordination environment of complex 2.The hydrogen atoms are omitted for clarity

Within an anion stack, the adjacent Ni(III) ions form a chain with the Ni··Ni distances being 3.564 and 3.895 ? through intermolecular Ni··S, S··S, Ni··Ni, etc, which have weak interactions.Extensive hydrogen-bonding interactions are also observed in complex 3.As shown in Fig.6b, the interactions among cations, anions and water molecules are found with the following distances: dN(5)··N(2G) = 2.920 ?, dO(1WE)··N(3F) = 2.941 ?, d(N5B)··O(1WC) = 2.938 ? and dO(1WE)··O(1WC) = 3.256 ? (Symmetry codes: B = 1–x, 1–y, 2–z; C = x, y, 1+z; E = 1–x, 1–y, 1–z; F = –x, 1–y, 1–z; G = –1+x, y, z).A 3-D supramolecular framework is formed through weak interactions.The anions and cations formed a segregated column in 3, as shown in Fig.6c.

Based on the same anionic unit [Ni(mnt)2]-by choosing different cations, different structures for complexes 1～3 are formed.The apparent differences are the distances with Ni··Ni and the resulted weak interactions.As discussed in complex 1, the distance of adjacent Ni(III) ions is 8.519 ?, and the construction of supramolecular structure is mainly through weak interactions among cations, anions and acetonitrile molecules.Complex 2 is similar to 1 and the 3-D formation is mainlythrough weak interactions between cations and anions.However, complex 3 is different from 1 and 2.As shown in 3, the distance of adjacent Ni(III) ions is closer than that in complexes 1 and 2, so the construction of supramolecular structures relies on the weak interactions not only among cations, anions and solvent molecules, but also among Ni··S, S··S and Ni··Ni.As can be seen from the above discussions, the weak interactions among the cations, anions and solvent molecules play an important role in constructing the supramolecular structures.The difference of cations leads to the different distances of Ni··Ni, which resulted in different weak interactions in complexes 1～3, and then led to changes in the structures.

Fig.5.Coordination environment of complex 3.The hydrogen atoms are omitted for clarity.Symmetry code: A = –x, –y+2, –z+2

Fig.6.(a) Side view of the anions stacking of complex 3 through Ni··Ni and S··S interactions.(b) Hydrogen bonding interactions between the cations, anions and water molecules.(c) Packing diagram for complex 3.Symmetry codes: B = 1–x, 1–y, 2–z; C = x, y, 1+z; D = 1+x, y, z; E = 1–x, 1–y, 1–z; F = –x, 1–y, 1–z; G = –1+x, y, z

3.2 UV-VIS properties

The UV-VIS spectra of complexes 1～3 in DMF with c = 10-5mol·L-1, as shown in Fig.7.The spectra of three complexes are similar.Several bands in the 200～400 nm region are mainly attributed to the π-π* transitions within the mnt2-in [Ni(mnt)2]-anion.The absorption bands at 482 nm for complex 1, 483 nm for complex 2 and 482 nm for complex 3 originate from the MLCT transition in the [Ni(mnt)2]-moiety[31].

4 CONCLUSION

In summary, three new complexes [AMP]-[Ni(mnt)2]·CH3CN (1), [DPI]2[Ni(mnt)2]I (2) and [DD][Ni(mnt)2]2·2H2O (3), have been synthesized.They exhibit segregated column struc- tures.UV-VIS properties of these three complexes are also investigated.The results further demon- strate different counter-cations could induce versatile stack modes and have a great influence on weak interactions.The work provides experimental basis for further study of maleonitriledithiolate complexes.Next work is in progress to explore new interesting structures and properties by the interactions of new cations with the ligand.

We thank Prof.Limin Zheng, Prof.Changsheng Lu, and Dr.Songsong Bao at Nanjing University for the physical property measurements and analyses of crystal structures.

Fig.7.UV-VIS spectra in DMF for complexes 1～3

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10.14102/j.cnki.0254-5861.2011-0704

4 March 2015; accepted 13 April 2015 (CCDC 1006014 for 1, 1006015 for 2 and 1003306 for 3)

① Supported by Basic & Advanced Technology Research Projects of Henan Science and Technology Department

② Corresponding author.Ph.D., mainly majoring in functional coordination chemistry.E-mail: yyu_yu@163.com