Cu(II)-Ln(III) (Ln = Gd, Tb and Dy) complexes of an unsymmetrical N2O3 donor ligand: field induced SMM behaviour of Cu(II)-Tb(III) complexes

Three new hetero-metallic CuII-LnIII complexes [(CuL)Gd(NO3)3(CH3OH)]n (1), [(CuL)Tb(NO3)3(H2O)]·[CuL] (2) and [(CuL)Dy(NO3)3(H2O)]·[CuL] (3) have been synthesized using a mono-nuclear Cu(II) complex, [CuL], of an unsymmetrically di-condensed N2O3 donor Schiff base ligand, N-(3-methoxysalicylidene)-N-(salicylidene)-1,2-ethylenediamine (H2L). Single crystal X-ray crystallography revealed that complex 1 is a nitrate bridged 1D chain of dinuclear Cu(II)-Gd(III) units whereas in 2 and 3, the dinuclear Cu(II)-Ln(III) units are co-crystallized with a [CuL] unit. The Ln(III) centers are nine coordinated with the geometry of a spherical capped square antiprism for Gd and spherical tricapped trigonal prism for Tb and Dy. The geometry of the Cu(II) center is distorted octahedral for complex 1 and distorted square planar for complexes 2 and 3. Temperature-dependent molar magnetic susceptibility measurements in 1-3 revealed the presence of overall ferromagnetic coupling between the Cu(II) and Ln(III) centers. Notably, field induced single-molecule magnet behavior was witnessed in the Tb(III) derivative (2). The ab initio calculations indicated that upon application of an external magnetic field, the tunneling in the ground state of complex 2 gets reduced and thereby field-induced SMM behaviour is observed. Besides, in the case of complex 1, BS-DFT calculations were carried out to gain further insights into the magnetic exchange coupling interactions between the Cu(II) and Gd(III) centers.

Synthesis, spectroscopic findings and crystal engineering of Pb(ii)-Salen coordination polymers, and supramolecular architectures engineered by σ-hole/spodium/tetrel bonds: a combined experimental and theoretical investigation

Spontaneous self-assembly is one of the available synthetic routes to achieve structurally versatile and unique crystal complexes with selected metal-ligand combinations in the spirit of pseudohalides. In this endeavour, we designed a novel 1D coordination polymer (CP), [(Cd)(Pb)(L)(η¹-NCS)(η¹-SCN)] _n (1), using a compartmental Salen ligand (H₃L) in the presence of NaSCN. The characterization of the CP was accomplished using several spectroscopic techniques: MALDI-TOF, PXRD, SEM, EDX mapping, and single-crystal X-ray crystallography. The CP crystallizes in the monoclinic space group P2₁/c with Z = 4. SCXRD reveals Cd(ii) and Pb(ii) metal ions fulfilled distorted square pyramidal and hemi-directed coordination spheres. Cd(ii) is placed in the inner N₂O₂ and heavier Pb(ii) in the outer O₄ compartments of the de-protonated form of the ligand [L]^2-. Supramolecular interactions in the intricate crystal structure produced attractive molecular architectures of the compound. The flexible aliphatic -OH pendent group coordinates with the Pb(ii) ions. This unique binding further elevates the supramolecular crystal topographies. The supramolecular interactions were authenticated by Hirshfeld surface analysis (HSA). The observation of the recurring unconventional tetrel bonds was rationalized by DFT calculations and surface plots of molecular electrostatic potential (MEP). In the 1D polymeric chain in the complex, the O-atom of the -OH groups shows a tetrel bonding interaction with the Pb atom. We have found that the combination of QTAIM/NCI and QTAIM/ELF plots helps reveal the nature of these contacts. Moreover, the QTAIM/ELF plot determines the donor-acceptor interaction between the O-atom and the Pb atom, establishing the σ-hole. Agreeably, the σ-hole interaction also helps Pb(ii) serve as a Lewis acid in the complex. Finally, spodium and tetrel bonds are formed, possible thanks to a hemi-directional coordination sphere of the Pb atoms in the polymer described.

Reaction of Cu(II) Chelates with Uranyl Nitrate to Form a Coordination Complex or H-Bonded Adduct: Experimental Observations and Rationalization by Theoretical Calculations

Four new heterometallic Cu(II)-U(VI) species, [{(CuL¹)(CH₃CN)}UO₂(NO₃)₂] (1), [{(CuL²)(CH₃CN)}UO₂(NO₃)₂] (2), [{(CuL³)(H₂O)}UO₂(NO₃)₂] (3), and [UO₂(NO₃)₂(H₂O)₂]·2[CuL⁴]·H₂O (4), were synthesized using four different metalloligands ([CuL¹], [CuL²], [CuL³], and [CuL⁴], respectively) derived from four unsymmetrically dicondensed N,O-donor Schiff bases. Single-crystal structural analyses revealed that complexes 1, 2, and 3 have a discrete dinuclear [Cu-UO₂] core in which one metalloligand, [CuL], is connected to the uranyl moiety via a double phenoxido bridge. Two chelating nitrate ions complete the octa-coordination around uranium. Species 4 is a cocrystal, where a uranyl nitrate dihydrate is sandwiched between two metalloligands [CuL⁴] by the formation of strong hydrogen bonds between the H atoms of the coordinated water molecules to U(VI) and the O atoms of [CuL⁴]. Spectrophotometric titrations of these four metalloligands with uranyl nitrate dihydrate in acetonitrile showed a well-anchored isosbestic point between 300 and 500 nm in all cases, conforming with the coordination of [CuL¹], [CuL²], [CuL³], and the H-bonding interaction of [CuL⁴] with UO₂(NO₃)₂. This behavior of [CuL⁴] was utilized to selectively bind metal ions (e.g., Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, and La³⁺) in the presence of UO₂(NO₃)₂·2H₂O in acetonitrile. The formation of these Cu(II)-U(VI) species in solution was also evaluated by steady-state fluorescence quenching experiments. The difference in the coordination behavior of these metalloligands toward [UO₂(NO₃)₂(H₂O)₂] was studied by density functional theory calculations. The lower flexibility of the ethylenediamine ring and a large negative binding energy obtained from the evaluation of H bonds and supramolecular interactions between [CuL⁴] and [UO₂(NO₃)₂(H₂O)₂] corroborate the formation of cocrystal 4. A very good linear correlation (r² = 0.9949) was observed between the experimental U═O stretching frequencies and the strength of the equatorial bonds that connect the U atom to the metalloligand.

Inorganic Molecular Complexes: Potential for Growth of a New Subject Area in Self-Assembly

The non-covalent assemblies among multiple non-identical metal complexes have scopes to develop a new subject area. There are infinite numbers of ways for different combinations among inorganic neutral or ionic complexes. Each partnering species of those molecular complexes would also have diversities by changing metal ions, ligands, oxidation states of metal ions, and coordination numbers. Keeping a view of the emergence of framework materials and self-assembled nano-structures of metal complexes, the non-covalently linked assemblies of inorganic molecular complexes would have scopes for new nano-dimensional materials. This account provides a systematic description of the different inorganic molecular complexes for a concerted effort to develop a new area that would have importance in applied materials.

Crystal structure of [4-chloro-2-(((2-((3-ethoxy-2-oxidobenzylidene)amino)phenyl)imino)(phenyl)methyl)phenolato-κ4 N,N′,O,O′}nickel(II) - ethyl acetate (1/1), C32H29ClN2NiO5

C32H29ClN2NiO5, triclinic, P1̄ (no. 2), a = 9.7657(5) Å, b = 10.1262(6) Å, c = 16.0745(9) Å, α = 83.025(2)°, β = 77.437(2)°, γ = 66.240(2)°, V = 1419.02(14) Å3, Z = 2, R gt(F) = 0.0403, wR ref(F 2) = 0.0908, T = 293(2) K.