Jing-Min Shi

Synthesis, crystal structure, and magnetism of a binuclear Cu(II) complex with double azido as asymmetric basal–apical end-on bridged ligand

A new binuclear copper(II) complex, [Cu2(μ1,1-N3)2(PP)2)] ⋅ 2ClO4 (PP = 2,6-dipyrazol-1-yl-pyridine), was synthesized with double azide as asymmetric end-on bridge ligand and 2,6-dipyrazol-1-yl-pyridine as the terminal ligand. The crystal structure was determined by X-ray crystallography. Cu(II) is located in a distorted square pyramidal geometry, and azide bridges the equatorial-axial linking two Cu(II) atoms with a separation of 3.3595(11) Å. The fitting for the data of the variable-temperature (2–300 K) magnetic susceptibilities by using the Curie–Weiss law gives the Weiss temperature θ = −7.830 K, indicating a very weak anti-ferromagnetic interaction between the bridging Cu(II) complexes.

Synthesis, crystal structure and magnetism of a two-dimensional Ni(II) coordination polymer with thiocyanate anion and dehydrogen-1,10-phenanthrolin-2-ol as bridging ligands

A two-dimensional coordination polymer [Ni(μ1,3-SCN)(μ-Pheno)(CH3OH)] n (where Pheno = dehydrogen-1,10-phenanthrolin-2-ol) has been synthesized and its crystal structure determined by X-ray crystallography. Adjacent Ni(II) ions are coordinated by μ1,3-SCN− and μ-Pheno alternately forming a two-dimensional sheet structure. The fitting of the variable-temperature magnetic susceptibilities with a binuclear nickel(II) formula reveals that there is an anti-ferromagnetic interaction between the bridging Ni(II) ions with the magnetic coupling constant 2J = −0.67 cm−1.

Synthesis, crystal structure and magnetism of a one-dimensional Cu(II) coordination polymer with monodeprotonated 2,2′-bypyridine-3,3′-diol as bridging ligand

A new one-dimensional copper(II) coordination polymer, [Cu(μ-HL)(H2O)2(NO3)] n (HL = monodeprotonated 2,2′-bypyridine-3,3′-diol), was synthesized and its crystal structure determined by X-ray crystallography. In the crystal Cu(II) is located a distorted octahedral coordination geometry and each HL coordinates two Cu(II) ions with its two N atoms and an O atom of deprotonated hydroxyl, giving a one-dimensional chain. The variable-temperature (2–300 K) magnetic measurements, analyzed using a one-dimensional Cu(II) magnetic interaction formula, indicate the existence of very weak ferromagnetic coupling with 2J = 0.014 cm−1.

π–π Stacking, hydrogen bonding and anti-ferromagnetic coupling mechanism on a mononuclear Cu(II) complex

Weak anti-ferromagnetic coupling is observed in a mononuclear copper(II) complex, [Cu(Pid)(OSO3)(H2O)] · (H2O) (Pid = 2,2′-(1,10-phenanthrolin-2-ylimino)diethanol). The Cu(II) complex is a distorted square pyramid. Analysis of the crystal structure indicates that there are two types of magnetic coupling pathways, where one pathway involves π–π stacking between adjacent complexes and the second one involves the O–H ··· O hydrogen bonds between adjacent complexes. The variable-temperature magnetic susceptibilities show that there is a weak anti-ferromagnetic coupling between adjacent Cu(II) ions with Curie–Weiss constant θ = −13.71 K = −9.93 cm−1. Theoretical calculations reveal that the π–π stacking resulted in anti-ferromagnetic coupling with 2J = −6.30 cm−1, and the O–H ··· O hydrogen-bonding pathway led to a weaker anti-ferromagnetic interaction with 2J = −3.38 cm−1. The theoretical calculations also indicate that anti-ferromagnetic coupling sign from the π–π stacking accords with the McConnell I spin-polarization mechanism.

Synthesis, crystal structure and magnetism of a one-dimensional MnII chain with a single μ 1,3-azido as bridge ligand

A new 1-D MnII chain, [Mn(μ 1,3-N3)(phenCl)2]n (ClO4)n (phenCl = 2-chloro-1,10-phenanthroline), was synthesized with single μ 1,3-azido as bridge and 2-chloro-1,10-phenanthroline as coligand, and its crystal structure determined by X-ray crystallography. In the complex, MnII is located in a distorted octahedral geometry, and azide is an end-end bridge, linking two MnII ions with separation of 5.7356(10) Å, forming a 1-D chain. In the crystal, there are two kinds of π-π stacking between adjacent chains. The fitting of the variable-temperature (2.00–320 K) magnetic susceptibilities gave an anti-ferromagnetic interaction of J = –5.99 cm–1 ( ), among the stronger magnetic interaction in MnII complexes with azido as single end-end bridge. Reported experimental results do not confirm clearly the magneto-structural correlations revealed by theoretical calculations.

π−π Stacking and magnetic coupling mechanism on a mononuclear Cu(II) complex

A mononuclear copper(II) complex was synthesized and in the crystal there are three types of π−π stacking interactions among adjacent complexes. The fitting for the data of the variable-temperature magnetic susceptibilities reveals that there is a weak anti-ferromagnetic coupling among adjacent Cu(II) ions with Weiss constant θ = −2.99 K = −2.08 cm−1. Theoretical calculations reveal that two types of π−π stacking resulted in anti-ferromagnetic couplings with 2J = −12.40 cm−1 and 2J = −9.74 cm−1, respectively, and the third type of π−π stacking led to a weak ferromagnetic interaction with 2J = 4.28 cm−1. The theoretical calculations also indicate that the ferromagnetic coupling sign from the π−π stacking accords with McConnell I spin-polarization mechanism, whereas the anti-ferromagnetic coupling signs cannot be explained with McConnell I spin-polarization mechanism.

Synthesis, crystal structure and magnetic behavior of a two-dimensional copper(II) complex with mellitic anion as bridging ligand

A two-dimensional complex Cu3[C6(COO)6](H2O)10 · 2H2O has been prepared and its crystal structure determined by X-ray crystallography. In the complex each mellitic anion provides four carboxylate groups as coordinate groups and, according to the coordination, the four carboxylate groups are classified as two types according to its coordinate modes. The first is that a carboxylate group coordinates a copper(II) ion via its one oxygen atom, and the second one is that a carboxylate group, as a two-dentate ligand, coordinates to two copper(II) ions. The copper(II) ions also are classified as being of two types according to their coordinate modes. The configuration around each copper(II) ion is a distorted pyramid. The variable-temperature magnetic susceptibility of the complex was measured in the 4–300 K range and the magnetic data indicate that the magnetic interaction between bridging copper(II) ions displays an antiferromagnetic coupling below 42 K, while above 42 K a ferromagnetic interaction appears.

Intermolecular interaction and magnetic coupling mechanism of a 2-D mixed-valence CuIICuI coordination polymer containing μ 1,1,3-SCN bridge

A 2-D CuICuII mixed oxidation state coordination polymer, [CuIICuI(μ 1,3-SCN)2(μ 1,1,3-SCN)(PhenE)] n (PhenE: 2-ethoxy-1,10-phenanthroline), has been prepared and its crystal structure determined by X-ray crystallography. In the polymer, CuII is a distorted trigonal bipyramidal geometry and CuI has distorted tetrahedral coordination. Thiocyanate bridges in two modes, μ 1,3-SCN and μ 1,1,3-SCN, resulting in a 2-D coordination sheet. The crystal structure analysis shows that there is a splipped π–π stacking in the sheet. The fitting for the variable-temperature magnetic susceptibility data gave the magnetic coupling constant 2J = −2.72 cm−1 and zJ′ = −2.07 cm−1. The magnetic interaction may be mainly ascribed to intermolecular π–π magnetic coupling.

Synthesis, crystal structure and magnetism of a 1-D polymeric manganese(II) complex with pyrazine-2-carboxylate as bridging ligand

A one-dimensional chain complex {[Mn(pyz)(SCN)(H2O)2] · H2O}∞ (pyz = pyrazine-2-carboxylic anion) has been synthesized and its crystal structure determined by X-ray crystallography. In the complex each Mn ion is located in a distorted octahedral environment with two oxygen atoms O(3), O(4) from terminal ligands of two water molecules, another oxygen atom O(1) from the carboxylate group of pyz, and three nitrogen atoms N(1), N(2A) from two different pyz units and N(3) from the terminal ligand thiocyanate anion, in which a chelated five-membered ring is formed by coordination of O(1) and N(1) to the Mn(1) atom. Thus, an infinite zigzag chain consisting of Mn and pyz is constructed and the chains are linked together by hydrogen bonding from coordinated and uncoordinated water molecules, the sulfur atom of thiocyanate and the carboxylate oxygen of pyz. The variable-temperature magnetic susceptibility of the complex was measured in the 4–300 K range. The magnetic coupling parameter is consistent with an antiferromagnetic exchange between the two manganese(II) centers and the data fit a binuclear magnetic exchange model based on the Hamiltonian operator (H = −2JS1S2, S1 = S2 = 5/2), giving the antiferromagnetic coupling parameter of 2J = −0.17 cm−1. This is the first pyrazine-2-carboxylic anion bridging complex dealing with the magnetic interaction study.

Synthesis, crystal structure, and magnetism of a 1-D CuII chain complex with a mono-bromide bridge

A 1-D CuII chain, [Cu(μ-Br)(phenmp)2]n·(ClO4)n (phenmp = 2-(4-methyl-pyrazol-1H-yl)-1,10-phenanthroline), was synthesized and its crystal structure was determined by X-ray crystallography. CuII is located in a distorted square-pyramidal geometry, with the mono-bromide – a bridge linking two adjacent CuII ions with a separation of 3.788 Å. The result is a uniform 1-D chain that lies along the c axis. Mono-halide-bridged models have not been reported very often. The fitting for the data of the variable-temperature (2.00–330 K) magnetic susceptibilities gave a ferromagnetic interaction of J = 5.11 cm−1 (H = −2JS 1 S 2) for adjacent-bridged CuII ions. Comparing mono-halide bridged CuII complexes, trigonal-bipyramidal geometry has strong magnetic interactions, whereas square-pyramidal geometry has weak magnetic interactions. In mono-bromide bridged CuII complexes, the Cu–Br–Cu angle is related to the magnetic coupling signs with small Cu–Br–Cu angle favoring ferromagnetic interaction, while large Cu–Br–Cu angle results in antiferromagnetic interactions.