A new two-dimensional manganese(II) coordination polymer with alternating double end-on and single end-to-end azido bridges: Crystal structure and magnetic properties

Dimerization of Paramagnetic Trinuclear Complexes by Coordination Geometry Changes Showing Mixed Valency and Significant Antiferromagnetic Coupling through -Pt···Pt- Bonds

Paramagnetic trinuclear complexes, trans-[Pt₂M(piam)₄(NH₃)₄](ClO₄)_x (t-M; piam = pivalamidate, M = Mn, Fe, Co, Ni, and Cu, x = 2 or 3), aligned as Pt-M-Pt were successfully synthesized and characterized. The dihedral angles between the Pt and M coordination planes in t-M are approximately parallel, showing straight metal-metal bonds with distances of approximately 2.6 Å. Except for t-Fe, the trinuclear complexes are dimerized with close contact (approximately 3.9 Å) between the end Pt atoms to form Pt-M-Pt···Pt-M-Pt alignments with high-spin M(+2) containing five (t-Mn), three (t-Co), two (t-Ni), and one (t-Cu) unpaired electrons localized on M atoms. Several physical measurements and calculations revealed that the dimerized structures were maintained in MeCN, where cyclic voltammograms for t-M exhibited two-step oxidation and reduction attributed to Pt-M(+2)-Pt···Pt-M(+2)-Pt ↔ Pt-M(+3)-Pt···Pt-M(+2)-Pt ↔ Pt-M(+3)-Pt···Pt-M(+3)-Pt via mixed-valent states. Magnetic susceptibility measurements for t-M showed antiferromagnetic interaction, t-Mn: J = -0.9 cm^-1, t-Co: J = -3.5 cm^-1, t-Ni: J = -7.3 cm^-1, and t-Cu: J = 0.0 cm^-1, between the two M centers with distances of 9.0 Å through Pt···Pt bonds.

Paramagnetic one-dimensional chains containing high-spin manganese atoms showing antiferromagnetic interaction through -Pt-Rh-Rh-Pt- bonds

To exploit the magnetic interactions of multiple metals, a heterometallic one-dimensional (1D) chain containing three kinds of metals, Rh, Pt, and Mn, where [Rh₂(O₂CCH₃)₄] and [Pt₂Mn(piam)₄(NH₃)₄]²⁺ (piam = pivalamidate) are connected through unbridged Rh-Pt bonds to form -Rh-Rh-Pt-Mn-Pt- alignments was successfully synthesized. The Mn atoms are tetrahedrally coordinated by four oxygen atoms of the piam ligands, where the coordination geometries form a zigzag 1D chain. Each Mn atom is linked by -Pt-Rh-Rh-Pt-, with a Mn-Mn separation of 13.9 Å. In parent [Pt₂Mn(piam)₄(NH₃)₄](PF₆)₂, Mn adopts two coordination environments, octahedral and tetrahedral, both of which are Mn(+2) high-spin states. In EtOH, [Rh₂(O₂CCH₃)₄] selectively binds tetrahedral Mn to afford a 1D chain. Physical analysis of the 1D chain using electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) revealed that all metals are divalent, indicating five unpaired spin-localized electrons on the Mn atoms. Magnetic susceptibility measurements indicated antiferromagnetic intra-chain interactions between the Mn atoms in the 1D chain, where χT at 300 K was 5.33 cm³ K mol^-1 and gradually decreased to 1.65 cm³ K mol^-1 at 2 K. Theoretical fitting of the magnetic behavior showed weak exchange coupling (zJ = -0.43 cm^-1) between two high-spin Mn(+2) ions through diamagnetic Pt-Rh-Rh-Pt.

Crystal structures, Hirshfeld surface analyses and thermal behavior of two new rare tetrahedral terminal zinc(ii) azide and thiocyanate Schiff base complexes

Crystal structures, Hirshfeld surface and thermal analyses of two new rare tetrahedral terminal zinc(ii) thiocyanate and azide Schiff base complexes of [ZnL(NCS)₂] and [ZnL(N₃)₂] are presented.