The thermal hysteresis in the cooperative spin crossover (SCO) polymer [Fe(trz)(Htrz) 2 ] n [BF 4 ] n (1) has been tuned by a simple ball milling grinding process. Mechanical treatment affects the size and morphology of the crystallite domains, as confirmed by multiple complementary techniques, including ESEM, DLS, and PXRD data. Upon milling, the regular cubic shape particles recrystallize with slightly different unit cell parameters and preferential orientation. This macroscopic change significantly modifies the thermally induced SCO behavior, studied by temperature-dependent magnetic susceptibility, X-ray diffraction, and DSC analysis. Transition temperatures downshift, closer to room temperature, while hysteresis widens, when particle sizes are actually decreasing. We relate this counterintuitive observation to subtle modifications in the unit cell, offering new alternatives to tune and enhance SCO properties in this class of 1Dcooperative polymers.

The potential access to Co IV species for promoting transformations that are particularly challenging at Co III still remains underexploited in the context of Cp*Co-catalyzed CÀ H functionalization reactions. Herein, we disclose a combined experimental and computational strategy for uncovering the participation of Cp*Co IV species in a Cp*Co-mediated C À S bond-reductive elimination. These studies support the intermediacy of high-valent Cp*Co species in CÀH functionalization reactions, under oxidative conditions, when involving nucleophilic coupling partners.

Bistable multifunctional materials have great potential in a large variety of devices, from sensors to information units. However, the direct exploitation of spin crossover (SCO) materials in electronic devices is limited due to their very high electrical resistance (insulators). Beyond their intrinsic properties, SCO materials may also work as probes to confer bistability as switchable components in hybrid materials, as controlled by external stimuli acting upon the SCO spin state. Low resistance conductors with memory effect may be obtained from the incorporation of SCO probes into a conducting organic polymer matrix. This strategy appeared to be limited by the strict synthetic conditions, since polymerization reactions are harsh enough to attack the redox‐unstable SCO component. Because of this, just a few successful examples have been reported. Here a versatile processing protocol is introduced to obtain SCO/conducting polymer composites exploiting a post‐synthetic mechanochemical approach that can be applied to any SCO component and any organic polymer. This new protocol allows highly conducting films of polypyrrole, polyaniline, and poly(3,4‐ethylenedioxythiophene) (PEDOT) to be obtained, with bulk conductivities as high as 1 S·cm−1, and exhibiting a thermal hysteresis in their electrical conductivity above room temperature.

No abstract

No abstract

In recent years, several examples of materials combining the molecular bistability of spin crossover (SC) and fluorescent moieties have flourished in the literature. Fluorescence is a sensitive probe, and SC may provide modulation of the signal, thus affording systems in which physicochemical changes in the environment of the SC centers could be effectively detected. On the contrary, organic semiconductor polymers are of great interest and, furthermore, have been successfully applied in different optoelectronic devices, such as transistors, solar cells, and light-emitting devices. Herein, we report on the fabrication of composites comprising a fluorescent, organic semiconductor polymer (polyfluorene) and a spin crossover compound, an Fe­(II)-triazole coordination polymer. A strong synergy was observed between the spin transition of the Fe­(II) compound and variations in the fluorescence of the organic polymer. The fluorescence modulation was shown to be reversible, with an increase of ≤20% with respect to the original value.

Here we present the synthesis, structure and magnetic properties of complexes of general formula (Mn)(Me2NH2)4][Mn3(μ-L)6(H2O)6] and (Me2NH2)6[M3(μ-L)6(H2O)6] (M = CoII, NiII and CuII); L−2 = 4-(1,2,4-triazol-4-yl) ethanedisulfonate). The trinuclear polyanions were isolated as dimethylammonium salts, and their crystal structures determined by single crystal and powder X-ray diffraction data. The polyanionic part of these salts have the same molecular structure, which consists of a linear array of metal(II) ions linked by triple N1-N2-triazole bridges. In turn, the composition and crystal packing of the MnII salt differs from the rest of the complexes (with six dimethyl ammonia as countercations) in containing one Mn+2 and four dimethyl ammonia as countercations. Magnetic data indicate dominant intramolecular antiferromagnetic interactions stabilizing a paramagnetic ground state. Susceptibility data have been successfully modeled with a simple isotropic Hamiltonian for a centrosymmetric linear trimer, H = −2J (S1S2 + S2S3) with super-exchange parameters J = −0.4 K for MnII, −7.5 K for NiII and −45 K for CuII complex. The magnetic properties of these complexes and their easy processing opens unique possibilities for their incorporation as magnetic molecular probes into such hybrid materials as magnetic/conducting multifunctional materials or as dopant for organic conducting polymers.

The potential access to Co IV species for promoting transformations that are particularly challenging at Co III still remains underexploited in the context of Cp*Co-catalyzed CÀ H functionalization reactions. Herein, we disclose a combined experimental and computational strategy for uncovering the participation of Cp*Co IV species in a Cp*Co-mediated C À S bond-reductive elimination. These studies support the intermediacy of high-valent Cp*Co species in CÀH functionalization reactions, under oxidative conditions, when involving nucleophilic coupling partners.