Satellite ligand effects on magnetic exchange in dimers. A structural, magnetic and theoretical investigation of Cu2L2X4 (L = methylisothiazolinone and X = Cl-, Br-).

Halide-bridged polymers have gained significant interest due to their diverse properties and potential applications. Stacked Cu2L2X4 dimers, where L is an organic ligand and X can be Cl- or Br-, are of interest because a chloride analogue where L = 2-pyridone, had previously been reported to exhibit bulk ferromagnetism, which augured great potentiality for this class of compounds. The synthesis, structural characterization, magnetic susceptibility measurements, and computational studies of two isostructural CuClMI (MI = methylisothiazolinone) and CuBrMI polymers of Cu(II), along with a related CuClPYR (PYR = 2-pyridone) is reported. CuClMI and CuBrMI were found to exhibit AFM bulk properties, due to FM/AFM alternating chains along the halide-bridged polymer axis, while FM bulk properties were confirmed for CuClPYR exhibiting a FM spin ladder. In combination with a benzamide analogue, CuClBA, three O-donor amides, CuClMI, CuClBA and CuClPYR were analyzed and revealed that the kinetic exchange is affected by the identity, but more importantly, the orientation of the satellite ligands. The torsional angle of the ligand with the dimer plane is shown to significantly affect the magnetic exchange in the dimer, and between dimers, explaining the reported FM bulk properties of CuClPYR. This finding is exceedingly important, as it suggests that a spin device can be constructed to flip between singlet/triplet states by manipulating the orientation of the satellite/terminal ligand.

Revisiting the Role of Hydrogen Bonding in the Strong Dimer Superexchange of a 2D Copper(II) Halide Honeycomb-Like Lattice: Structural and Magnetic Study.

The title compound H2L(CuCl3H2O)Cl (H2L = 1-(4'-pyridinium)pyridin-4-ol-ium), 1) was synthesized and investigated structurally and magnetically as well as via a first-principles, bottom-up theoretical analysis of the potential magnetic superexchange pathways. Compound 1 can be described structurally as a well-isolated, distorted 2D-honeycomb lattice with two potential exchange pathways: a dimeric interaction via hydrogen-bonded pairs of (CuCl3H2O) ions and a chain structure via bridging chloride ions. Surprisingly, the experimental magnetic data are best fitted using both a simple dimer model with a Curie-Weiss correction for interdimer exchange (Jdimer = -107.4(1) K, θ = -1.22(4) K) and a strong-rung ladder model (Jrung = -105.8(7) K, Jrail = 2(7) K). Theoretical analysis at the UB3LYP/6-31+G(d) level supports the strong exchange observed through the [CuCl4(H2O)]2- dimer moiety superexchange pathway (-102 K = -71 cm-1). However, the apparent vanishingly small exchange through the single halide bridge is merely a brute average of competing ferromagnetic (FM) (+24.8 K = +17.0 cm-1) and antiferromagnetic (AFM) (-21.0 K = -14.6 cm-1) exchange interactions. Our computational study shows that these fitting parameters carry no physical meaning since a honeycomb plaquette must be taken as magnetic building block for 1. The competition between FM and AFM pair interactions leads to geometrical frustration in 1 and could induce interesting magnetic response at low temperatures, if the magnetic exchange is adequately tuned by modifying substituents in ligands and, in turn, interactions within the crystal packing.

3-Methyl-anilinium nitrate.

In the title compound, C(7)H(10)N(+)·NO(3) (-), the 3-methyl-anilinium cations inter-act with the nitrate anions through strong bifurcated N(+)-H⋯(O,O) hydrogen bonds, forming a two-dimensional hydrogen-bonded network.

Bis(4-amino-benzoic acid-κN)dichloridozinc(II).

Mol-ecules of the title compound [ZnCl(2)(C(7)H(7)NO(2))(2)], are located on a twofold rotation axis. Two 4-amino-benzoic acid moieties, and two chloride ligands are coordinated to a Zn atom in a tetra-hedral fashion, forming an isolated mol-ecule. Neighbouring mol-ecules are linked through hydrogen-bonded carboxyl groups, as well as N-H⋯Cl hydrogen-bonding inter-actions between amine groups and the chloride ligands of neighbouring mol-ecules, forming a three-dimensional network.

Bis(2-methyl-4-nitro-anilinium) tetra-chloridomercurate(II).

The title compound, (C(7)H(9)N(2)O(2))(2)[HgCl(4)], self-assembles into cationic organic bilayers containing the 2-methyl-4-nitro-anilinium cations, sandwiched between anionic inorganic layers built up by the distorted tetra-hedral [HgCl(4)](2-) groups. The organic sheets are inter-linked through weak C-H⋯O hydrogen bonds, while they inter-act with the anionic part via strong charge-assisted N(+)-H⋯Cl-Hg hydrogen bonds. The [HgCl(4)](2-) anions are bis-ected by a mirror plane passing through the metal and two of the chloride ions.

Bis(1-phenylethylammonium) hexachloridostannate(IV) and bis(2-phenylethylammonium) hexachloridostannate(IV).

The crystal structures of the two isomers bis(1-phenylethylammonium) hexachloridostannate(IV) and bis(2-phenylethylammonium) hexachloridostannate(IV), both (C(8)H(12)N)(2)[SnCl(6)], exhibit alternating organic and inorganic layers, which interact via N-H...Cl hydrogen bonding. The inorganic layer contains an extended two-dimensional hydrogen-bonded sheet. The Sn atom in the 1-phenylethylammonium salt lies on an inversion centre.

Bis(benzylammonium) hexachlorotin(IV).

The crystal structure of bis(benzylammonium) hexachlorotin(IV), (C(7)H(7)NH(3))(2)[SnCl(6)], exhibits ionic layers separated by hydrocarbon layers. The hydrocarbon layer contains two crystallographically inequivalent benzyl groups and aromatic pi-pi stacking interactions are observed in this layer. In the inorganic layer, the ammonium groups interact with isolated tilted [SnCl(6)](2-) octahedra through normal, bifurcated and trifurcated N-H.Cl hydrogen bonds.