Materials combining bio-based resource and degradability aspects such as polylactide (PLA) can represent a sustainable alternative to commercially used oil-based plastics. With tin octanoate (Sn(Oct)(2)) as the catalyst of choice for industrial scale PLA production, traces of the toxic heavy metal can be released into the environment, rendering PLA unsuitable for specific applications. Herein we present four new homoleptic zinc Schiff base complexes that offer facile synthesis and can be handled under aerobic conditions. These robust, tetra-coordinated complexes have been tested as catalysts for the ring-opening polymerization (ROP) of lactide and are well suited under industrially relevant conditions. In situ Raman spectroscopy has been used to determine the apparent reaction rate constant (k(app)) for all complexes at 150 degrees C in bulk. For the fastest complex a k(p) of 3.66 +/- 0.14 x 10(-2) L mol(-1) s(-1) was additionally determined. For this catalyst, 71% conversion and a number-averaged molar mass of above 90000 g mol(-1) has been reached within less than 30 min at a monomer-to-initiator ratio ([M]/[I]) of 1000:1. The good polydispersity (D = 1.7) indicates a controllable ROP via the coordination-insertion mechanism (CIM).

Bistable spin crossover complexes such as [Fe{HB(pz)(3)}(2)] (pzH = pyrazole) show promise for sensor applications and electrically-controlled data storage units, but exploiting their potential hinges on their integration into a functional environment. We here present a system enabling such covalent post-functionalization steps in both symmetric and asymmetric patterns, based on the amine-functionalized complex [Fe{HB(4-NH(2)pz)(pz)(2)}(2)], obtained by reduction of the nitro analogue. The building block aspects of [Fe{HB(4-NH(2)pz)(pz)(2)}(2)] are showcased by its transformation into amide, imine and azo derivatives, which are structurally and magnetically characterized. All tris(pyrazolyl)borate complexes retain the spin crossover properties of their parent compound, with spin crossover temperatures ranging from 350 to 430 K. The transition parameters are correlated with the electronic properties of the functionalizing group, opening the possibility of fine-tuning the spin crossover properties of the building block as it is integrated in the environment of choice.

Invited for the cover of this issue is the group of Paul Kögerler from RWTH Aachen University, Germany. The cover image shows an aluminum sheet painted with thermochromic lacquer based on functionalized derivatives of iron(II) bis(tris(pyrazolyl)borate) complexes.

The Front Cover shows an aluminum sheet painted with thermochromic lacquer based on functionalized derivatives of a traditional spin-crossover staple, namely iron(II) bis(tris(pyrazolyl)borate) complexes. Facile, controlled pyrazole metathesis allows us to introduce various functional groups, exemplified here by three nitro derivatives. This enables a slew of post-reactions, ranging from reduction to the corresponding amines to the subsequent introduction of thioether residues, with the perspective of covalently anchoring such complexes to various environments. We thank Dominion Colour Corporation for their support in preparing the experimental lacquer coating. More information can be found in the Communication by P. Kögerler, C. Besson et al. For more on the story behind the cover research, see the Cover Profile.

A homovalent coordination cluster, [Ca-10(II)(OH)(2)(bda)(6)(ib)(6)] (1), featuring a nearly planar, hexagonal {Co-10} array composed of ten edge-sharing {Co-3(mu(3)-O)} triangles, forms in a nearly quantitative reaction as solvothermal decomposition product of the heterovalent pentanuclear precursor [(Co3Co2II)-Co-II(Hbda)(2)(bda)(2)(ib)(6)] (ib: isobutyrate; H(2)bda: N-butyldiethanolamine) in DMSO. 1 crystallizes in the triclinic space group P-1 (a = 7.4200(15) angstrom, b = 9.773 (2)angstrom, c = 11.601(2) angstrom, alpha = 105.38(3)degrees, beta = 106.32(3)degrees, gamma = 93.38(3)degrees). The use of the {(Co3Co2III)-Co-II} precursor, in combination with autogenous pressure, was found to be crucial for the condensation process yielding 1, which cannot be obtained by analogous reactions of the ligands and Co-II salts in DMSO. Magnetic ac and dc susceptibility data of 1 reveal dominant ferromagnetic exchange interactions, but no slow magnetization relaxation.

Graphical Abstract A rare case of supramolecular magnetism is observed in {V22O54(X)}-type mixed-valence polyoxovanadate(IV/V) host–guest systems. Here diamagnetic anionic guest species, although only in weak electrostatic contact with the surrounding polyoxovanadate host shell, strongly affect the V(3d) spin density distribution and magnetic coupling. For more details, see the Full Paper by K. Yu. Monakhov, P. Kögerler, and co-workers on page 2387 ff.

Mixed-valence polyoxovanadates(IV/V) have emerged as one of the most intricate class of supramolecular all-inorganic host species, able to encapsulate a wide variety of smaller guest templates during their self-assembly formation process. As showcased herein, the incorporation of guests, though governed solely by ultra-weak electrostatic and van der Waals interactions, can cause drastic effects on the electronic and magnetic characteristics of the shell complex of the polyoxovanadate. We address the question of methodology for the magnetochemical analysis of virtually isostructural {V(IV/V) 22 O54 }-type polyoxoanions of D2d symmetry enclosing diamagnetic VO2 F2 (-) (C2v ), SCN(-) (C∞v ), or ClO4 (-) (Td ) template anions. These induce different polarization effects related to differences in their geometric structures, symmetry, ion radii, and valence shells, eventually resulting in a supramolecular modulation of magnetic exchange between the V(3d) electrons that are partly delocalized over the {V22 O54 } shells. We also include the synthesis and characterization of the novel [V(V) O2 F2 @HV(IV) 8 V(V) 14 O54 ](6-) system that comprises the rarely encountered discrete difluorovanadate anion as a quasi-isolated guest species.

Mixed-valence polyoxovanadates(IV/V) have emerged as one of the most intricate class of supramolecular all-inorganic host species, able to encapsulate a wide variety of smaller guest templates during their self-assembly formation process. As showcased herein, the incorporation of guests, though governed solely by ultra-weak electrostatic and van der Waals interactions, can cause drastic effects on the electronic and magnetic characteristics of the shell complex of the polyoxovanadate. We address the question of methodology for the magnetochemical analysis of virtually isostructural {V(IV/V) 22 O54 }-type polyoxoanions of D2d symmetry enclosing diamagnetic VO2 F2 (-) (C2v ), SCN(-) (C∞v ), or ClO4 (-) (Td ) template anions. These induce different polarization effects related to differences in their geometric structures, symmetry, ion radii, and valence shells, eventually resulting in a supramolecular modulation of magnetic exchange between the V(3d) electrons that are partly delocalized over the {V22 O54 } shells. We also include the synthesis and characterization of the novel [V(V) O2 F2 @HV(IV) 8 V(V) 14 O54 ](6-) system that comprises the rarely encountered discrete difluorovanadate anion as a quasi-isolated guest species.

One-dimensional chain coordination polymers based on hexanuclear iron(III) pivalate building blocks and 1,4-dioxane (diox) or 4,4'-bipyridine (4,4'-bpy) bridging ligands, [Fe6O2(O2CH2)(O2CCMe3)12(diox)]n (1) and [Fe6O2(O2CH2)(O2CCMe3)12(4,4'-bpy)]n (2), showcase the utility of the angular overlap model, implemented in the program wxJFinder, in the predictive identification of the relative role of intra- and intercluster coupling.