Ligand Modulation of the Structures and Magnetic Relaxation in Triangular Dy3 Complexes Based on a Tricompartmental Scaffold

Using a novel tricompartmental hydrazone ligand, a set of trinuclear Dy₃ complexes has been isolated and structurally characterized. Complexes Dy₃  ⋅ Cl, Dy₃  ⋅ Br, and Dy₃  ⋅ ClO₄ feature a similar overall topology but different anions (Cl^- , Br^- , or ClO₄ ^- ) in combination with exogenous OH^- and solvent co-ligands, which is found to translate into very different magnetic properties. Complex Dy₃  ⋅ Cl shows a double relaxation process with fast quantum tunneling of the magnetization, probably related to the structural disorder of μ₂ -OH^- and μ₂ -Cl^- co-ligands. Relaxation of the magnetization is slowed down for Dy₃  ⋅ Br and Dy₃  ⋅ ClO₄ , which do not show any structural disorder. In particular, fast quantum tunneling is suppressed in case of Dy₃  ⋅ ClO₄ , resulting in an energy barrier of 341 K and magnetic hysteresis up to 3.5 K; this makes Dy₃  ⋅ ClO₄ one of the most robust air-stable trinuclear SMMs. Magneto-structural relationships of the three complexes are analyzed and rationalized with the help of CASSCF/RASSI-SO calculations.

Construction of Zn(II) Linear Trinuclear Secondary Building Units from A Coordination Polymer Based on α-Acetamidocinnamic Acid and 4-Phenylpyridine

The synthesis and characterization of one coordination polymer and two trinuclear complexes are presented. The coordination polymer [Zn2(µ-O,O'-ACA)2(ACA)2(4-Phpy)2]n (1) has been obtained by the reaction between Zn(OAc)2·2H2O, α-acetamidocinnamic acid (HACA), and 4-phenylpyridine (4-Phpy) using EtOH as solvent. Its recrystallization in CH3CN or EtOH yields two trinuclear complexes, both having pinwheel arrays with formulas [Zn3(µ-ACA)6(4-Phpy)2]·4CH3CN (2·4CH3CN) and [Zn3(µ-ACA)6(EtOH)2]·4EtOH (3·4EtOH), respectively. These trinuclear species, unavoidably lose their solvent co-crystallized molecules at RT yielding the complexes [Zn3(µ-ACA)6(4-Phpy)2] (2) and [Zn3(µ-ACA)6(EtOH)2] (3). In addition, compound 2 has also been obtained reacting Zn(OAc)2·2H2O, HACA, and 4-Phpy in a 1:2:2 ratio using CH3CN as solvent. Compounds 1-3 have been characterized by analytical and spectroscopic techniques. Furthermore, single crystals suitable for X-ray diffraction method for compounds 1, 2·4CH3CN, and 3·4EtOH were obtained and their supramolecular interactions have been studied and discussed, showing 2D supramolecular planes for the trinuclear complexes and a 3D supramolecular network for the coordination polymer. Finally, the supramolecular interactions of 2·4CH3CN and 3·4EtOH have been compared using Hirshfeld surface analysis and electrostatic potential calculations.

Multimetallic and Mixed Environment Iridium(III) Complexes: A Modular Approach to Luminescence Tuning Using a Host Platform

Mononuclear and trinuclear bis‐cyclometallated Ir^III complexes of the host ligands tris(4‐[4′‐methyl‐2,2′‐bipyridyl]methyl)cyclotriguaiacylene (L1) and tris(4‐(4′‐methyl‐2,2′‐ bipyridyl)carboxy)cyclotriguaiacylene (L2) have been prepared. Complexes [{Ir(ppy)₂}₃(L1)](PF₆)₃ (1.1), [{Ir(ppy)₂}(L1)](PF₆)₃ (1.2), [{Ir(ppy)₂}₃(L2)](PF₆)₃ (2.1) and [{Ir(ppy)₂}(L2)](PF₆)₃ (2.2) (where ppy=phenylpyridinato) showed distinct photophysical properties depending on the L ligand. Complexes featuring the L1 ligand were comparatively blue‐shifted in solution, with longer lifetimes and higher quantum yields. The mixed bis‐cyclometallated Ir^III complexes [{Ir(ppy)₂}{Ir(dFppy)₂}₂(L1)](PF₆)₃ (1.3), [{Ir(ppy)₂}{Ir(dFppy)₂}₂(L2)](PF₆)₃ (2.3), [{Ir(ppy)₂}₂{Ir(dFppy)₂}(L1)](PF₆)₃ (1.4) and [{Ir(ppy)₂}₂{Ir(dFppy)₂}(L2)](PF₆)₃ (2.4) (where dFppy=2,4‐difluorophenylpyrinato) were also synthesised. Steady‐state and time‐resolved spectroscopy, along with electrochemical investigations, show that the Ir(III) chromophores within these mixed Ir‐environment species behave as isolated centres, with no energy transfer or electronic communication between them.

Structural Preferences in Phosphanylthiolato Platinum(II) Complexes

The transition‐metal complexes of heterotopic phosphanylthiolato ligands are useful in various reactions which depend on the stereochemistry of the complexes. Bis‐chelate complex [Pt(SCH₂CH₂PPh₂‐κ²P,S)₂] (1) was obtained in good yields by direct base‐free substitution reaction of the corresponding phosphanylthiol (HSCH₂CH₂PPh₂) with K₂PtCl₄ or by oxidative addition of the same phosphanylthiol to Pt(PPh₃)₄. In agreement with the antisymbiosis rule, complex 1 shows a cis‐P,P arrangement in solid state crystallizing in the monoclinic system (C2/c). Density functional theory (DFT) calculations on 1 reveal the right characteristics for the preferred cis‐P,P arrangement, rationalizing its formation. Direct base‐free reaction of [PtCl₂(1,5‐cyclooctadiene)] with one equivalent of the same phosphanylthiol produce the trinuclear complex [PtCl(μ‐SCH₂CH₂PPh₂‐κ²P,S)]₃ (2) instead of the binuclear structure common in palladium and nickel derivatives. Crystals of 2 are triclinic (P1‾ ) showing a sulfur‐bridging edge‐sharing cyclic trinuclear complex with square‐planar coordination geometry around the platinum atoms and a Pt₃S₃ cycle in skew‐boat conformation. This preference for the trinuclear structure was rationalized mechanistically and through conceptual DFT.

Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt(0) Complex, via Novel Pt-Zn and Pt-Hg Compounds

The thermally stable [(tBuMe2 Si)2 M] (M=Zn, Hg) generate R3 Si(.) radicals in the presence of [(dmpe)Pt(PEt3 )2 ] at 60-80 °C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations.