Synthesis and structural characterization of Mn(II) and Cu(II) complexes with bis(4-(1H-imidazol-1-yl)phenyl)methanone ligands

2.1 Preparation and characterization of the complexes

When the metal precursors M(hfac)₂ (M=Mn, Cu) were reacted with BIPMO in EtOH-dichloromethane at room temperature, coordination polymers were obtained in good yields (82%–86%). The complexes are stable in common solvents such as benzene, hexane, ethanol, and dichloromethane.

The composition of 1 and 2 was confirmed by infrared (IR) spectroscopy and elemental analyses. The IR spectra of 1 and 2 were consistent with their formulation. Weak IR bands centered at ca. 3150 cm⁻¹ can be assigned to ν(C–H) of the ligands. A large group of bands in the region 1610–1430 cm⁻¹ are characteristic of ν(C=N) and ν(C=C) stretches of aromatic groups.

2.2 Molecular structures of 1 and 2

The structures of 1 and 2 have been determined by single-crystal X-ray diffraction (Table 1). Selected bond lengths and angles for 1 and 2 are listed in Table 2. The Ortep drawings of 1 and 2 are shown in Figs. 1 and 2, respectively. The results of single-crystal X-ray diffraction analyses indicate that the structures of complexes 1 and 2 are similar. Accordingly, the structure of 1 is described representatively here in more detail. Complex 1 crystallizes in the monoclinic space group P2₁/c and the asymmetric unit consists of one Mn(II) atom, one BIPMO, and two hfac ligands. As shown in Fig. 1, each Mn(II) ion is in a distorted octahedral geometry, coordinated by two pairs of oxygen atoms (O2, O3 and O4, O5) from two chelating hfac ligands and two nitrogen atoms (N1 and N4#1) from two BIMPO ligands. The Mn–O distances range from 2.146(2) to 2.259(2) Å, while the Mn–N ones are 2.190(2) and 2.210(2) Å, and the coordination angles around Mn1 are in ranges near 90° and 180°. The BIPMO ligand is V-shaped with a C7–C10–C11 angle of 119.9(2)°. Each BIPMO acts as a bridging ligand to link two Mn(II) atoms to form a helical chain with Mn···Mn distances of 17.346(1) Å and Mn···Mn···Mn angles of 77.30° running along the c axis (Fig. 3). Furthermore, in complex 1, the helical chains are further connected by C–H···O and C–H···F hydrogen bonds, and F···π, C–H···π, π···π, and F···F interactions to produce a three-dimensional (3D) framework (Fig. 4 and Table 3).

Fig. 1:

Coordination environments of complex 1 showing 30% probability ellipsoids. The hydrogen atoms are omitted for clarity. Symmetry code: ^#1–x, y–1/2, –z+1/2.

Fig. 2:

Coordination environments of complex 2 showing 30% probability ellipsoids. The hydrogen atoms are omitted for clarity. Symmetry code: ^#1–x–1, y–1/2, –z+1/2.

Fig. 3:

View of the helical chain along the c axis of 1 (a) and 2 (b). The adjacent distances of Mn···Mn is 17.346 Å and the distance Cu···Cu is 17.087 Å.

Fig. 4:

(a) View of the helical chain of 1 viewed along the c axis; (b) packing diagram of 1 viewed along the a axis.

4.1 Materials and measurements

All solvents and reagents were purchased from Aladdin Industrial Corporation of Shanghai, P.R. China. BIPMO was synthesized according to the literature method [12]. Melting points are uncorrected. Elemental analyses were performed on an Elementar Vario ELIII elemental analyzer. The IR spectra were recorded on a Bruker Vector 22 spectrophotometer with KBr pellets in the 4000–400 cm⁻¹ region.

4.2 X-ray crystallography

All measurements were made on an Agilent Technology SuperNova Eos Dual system with a MoK_α micro focus source (λ=0.71073 Å) and focusing multilayer mirror optics. The data were collected at a temperature of 293 K and processed using CrysAlisPro [13]. Absorption corrections were applied using the SADABS program [14]. The structures were solved by Direct Methods [15] with the Shelxtl (version 6.10) program [15], [16] and refined by full matrix least-squares techniques on F² with Shelxtl [15], [16]. All non-hydrogen atoms were refined anisotropically. The ligand hydrogen atoms were localized in their calculated positions and refined using a riding model. In the structure of 2, command DELU was used to atoms Cu1, O2, O4, and O5 with Hirshfeld errors.

CCDC 1451115 and 1451116 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif.