Four heteroleptic copper(II) complexes with the composition Cu(SQ)(L) containing two different ligands: 3,6di-tert-butyl-o-benzosemiquinonate radical-anion (SQ) and formazanate anion (L) were synthesized by the interaction of Cu(SQ)2 with neutral formazans (LH). The formazanate ligands were varied in terms of the nature of R-substituents in the R3-& Scy; position of the formazan backbone (R3= phenyl/p-tolyl/nitro groups) and N-Ar groups (Ar= phenyl/p-tolyl). All complexes were characterized by single-crystal X-ray diffraction. The monomeric compounds exhibit a flattened, pseudo-tetrahedral coordination geometry, wherein the degree of distortion of the coordination node depends on R3-substituents of the formazanate ligand. Bond lengths in the coordination core indicate a Cu(II)(SQ)(L) charge distribution, which is supported by Cu K-edge X-ray absorption spectroscopy data. Computational data reveal that the distortion toward tetrahedral geometry in the fourcoordinate Cu(II)(SQ)(L) complexes arises from the contribution of a Cu(I)(Q)(L) resonance structure. The complexes demonstrate diamagnetic properties due to strong intramolecular antiferromagnetic metal-ligand exchange. The reduction behavior, as measured by cyclic voltammetry, depends on the substituent at the R3-C position of the formazanate ligand. The UV/Vis absorption spectra feature bands associated with ligand-based transitions.

In this paper, we consider a series of new compact A-π-D photoinitiators consisting of donor aromatic fragments (naphthalene, anthracene, phenanthrene, pyrene and perylene) and a strong acceptor tricyanoethylene group—aryltricyanoethylenes (ArTCNEs). Spectral, photophysical, and electrochemical characteristics of ArTCNEs are studied. One-photon (with LED@405 nm) and two-photon (λ = 780 nm, impulse duration of 100 fs) photopolymerization of PETA can be effectively initiated by ArTCNEs with the tertiary amine N,N-dimethylcyclohexylamine DMCHA and/or the iodonium salt diphenyliodonium chloride Iod. Based on results of experiments on photodegradation, photopolymerization and EPR spectroscopy, a photoinitiation mechanism of radical photopolymerization was proposed for two-component (AntTCNE/DMCHA) and three-component (AntTCNE/DMCHA/Iod) initiating systems. The composition containing PerTCNE/DMCHA as a photoinitiator demonstrated the best reactivity under two-photon nanolithography conditions: the polymerization threshold was 2 mW at a laser beam scanning speed of 100 μm/s, and the widest fabrication window of 11 mW was typical for it. As an example, 3D “cage” structures were fabricated using the AntTCNE-based composition, and the test structure resolution parameters, such as the minimum line width and the distance between lines of 80 and 400 nm, respectively, were achieved. MTT experiments with human dermal fibroblasts showed promising preliminary biocompatibility of the resulting polymers, which opens up possibilities for using the obtained materials in biological applications.

A series of trialkyl-substituted o-benzoquinones has been synthesized and studied. This class of compounds are Norish II-type photoinitiators used in photo-curing technology. Their reactivity in photoreduction and polymerization inhibition reactions is determined. The photoinitiating properties of this series of o-benzoquinones in the presence of N,N-dimethylethanolamine (DMAE) were studied using the example of cured dimethacrylate resins (OCM-2, TEGDMA) under irradiation with light >500 nm. Changing the alkyl substituents in position 6 from primary (Q(6)(Et), Q(7)(Me)) to tertiary (Q(1)(Ad)-Q(3)(t-Bu)) significantly increases the efficiency of o-quinones as photoinitiators, in particular, the maximum rate of photopolymerization of TEGDMA increases by 8 times. Quinone Q(3)(t-Bu) proved to be the most effective photoinitiator among the obtained derivatives and is a more effective initiator than the well-known 3,6-di-tert-butyl-o-benzoquinone in both TEGDMA and OCM-2. Furthermore, the photoinitiating systems based on o-quinone/amine has effective photobleachable and low absorbtion in the 500-650 nm region, which is promising for their use for curing thick films. Thick samples of poly TEGDMA (3.5 cm thickness) with and without the additional yellow or red dyes were obtained from PCC based on Q(3)(t-Bu)/DMAE by irradiating the LED Warm White (25 mW/cm(2)) for 20 min.

Oxidation of complexes [(dpp-bian)M(THF)n] (M = Mg, n = 3; M = Ca, n = 4) with 1 molar equivalent of iodine and then a treatment of the in situ formed dpp-bian radical-anionic species [(dpp-bian)MI(THF)n] (M = Mg, Ca) with potassium isopropoxide afforded [(dpp-bian)Mg(OiPr)]2 and [(dpp-bian)Ca(OiPr)(THF)][(dpp-BIAN)Ca(OiPr)], which were isolated as deep red crystals and characterized by spectroscopic methods. Molecular structures of the prepared complexes were determined by the single crystal X-ray analysis. Polymerization of lactide in the presence of complexes was carried out in toluene under argon at 90°C for 2 h. In all the cases the conversion of monomer reached >90

Two new A-pi-D-type photoinitiators based on indane-1,3-dione with methacrylate Dye 2 and isobutyrate Dye 3 groups were synthesized and characterized by NMR, IR- and UV-Vis spectroscopy. The spectral, photoluminescent and electrochemical properties of Dye 2 and Dye 3 compounds were investigated. Compounds Dye 2 and Dye 3 with tertiary amines N,N-dimethylaniline (DMA), N,N-dimethylcyclohexylamine (DMCHA) initiate both one- (LED with lambda = 405 nm) and two-photon (lambda = 780 nm and scale of impulse duration 100 fs) photopolymerization of PETA. The polymerization threshold of the Dye 2-based composition (Dye 2-DMA-PETA) under two-photon initiation conditions was 6.5 mW at a scanning speed of 100 mu m/s. Cage-like scaffold structures were fabricated by DLW-nanolithography using Dye 2 and Dye 3-based compositions. Structures with a line thickness of 90 nm located at a distance of 220 nm were obtained from the Dye 2-DMCHA-PETA composition, and for the Dye 3-DMCHA-PETA composition lines with a thickness of 140 nm at a distance of 310 nm were obtained. Due to the presence of methacrylate groups, Dye 2 has the ability to link into polymer networks and improves the thermal and physical-mechanical characteristics of polymers and increases the printing resolution under two-photon photopolymerization conditions. Additionally, it reduces the migration of the photoinitiator from the polymer matrix, compared to Dye 3. These advantages will allow the development of photopolymerizable compositions and biocompatible polymers based on them with high thermal stability and physical and mechanical characteristics.

Multistability on the molecular scale level required for molecular devices can be realized using metallocomplexes with redox-active ligands such as o-quinones, o-quinoneimines and o-diimines as building blocks. Herein, we prepared four sterically shielded di-o-quinones bridged with a dioxyarylene linker with different topology and steric characteristics and studied the properties of their reduced species. EPR spectroscopy investigation revealed that the intramolecular exchange interaction between paramagnetic centers in the biradical dianion derivatives of synthesized di-o-quinones predominantly depends on the steric environment of the linker and the nature of the counter cation at the dioxolene site, and the topology of the linker plays a secondary role.

Bis-3,6-di-tert-butyl-o-benzosemiquinonato cobalt complex with tris(2,6-dimethoxyphenyl)phosphine was synthesized and characterized. Single crystal X-ray diffraction studies indicate a highly distorted square-pyramidal coordination environment of cobalt. Phosphorus atom lies in the base of pyramid. Coordination geometry essentially changes with cooling. Magnetic measurements and DFT calculations indicate quartet ground state at both temperatures (100 and 298 K). Quantum-chemical study has showed that significant variation of exchange interaction energies between spins of paramagnetic centers occurs with lowering temperature.

Neodymium and dysprosium perylene complexes LnI(Per)(DME) 2 ⋅Per (Ln = Nd, Dy) were obtained for the first time by the reaction of the Ln diiodides with perylene in dimethoxyethane. The structure of dysprosium complex was established by X-ray diffraction (CCDC no. 2184200). Experimental–theoretical electron density analysis was performed to specify the type of coordination between the dysprosium cation and perylene in DyI(Per)(DME) 2 ⋅Per. Despite the identical composition, the Nd and Dy complexes have different structures, which is reflected in their luminescence properties.

Three novel five-coordinated bis-dioxolene cobalt complexes were synthesized and characterized by single crystal X-ray diffractometry and magnetochemistry. Structural study indicates square-pyramidal coordination geometry around cobalt ion. Structural parameters of coordinated dioxolenes together with magnetic measurements and DFT calculation data characterize compounds as mixed valence catecholato-semiquinonate derivatives of low spin cobalt(III). Magnetic moment of complex based on methoxy-substituted dioxolene grows at the temperatures above 260 K that can be interpreted as valence tautomeric/spin-crossover transition. This transition is not completed at the temperature 350 K.

The exchange reaction of equimolar amounts of the potassium radical anion salt of diazabutadiene [DADMe•−K(THF)n] (1) (DADMe = DippNC(Me)C(Me)NDipp; Dipp = = 2,6-Pri2C6H3) with anhydrous ScCl3 and NdCl3 afforded the dichloride complexes [DippN=C(Me)C(=CH2)NDipp]LnCl2(THF)2 (Ln = Sc (3), Nd (4)) in 75

The potassium salt of the perylene ligand used as a precursor in further transformations was obtained by the reduction of perylene with potassium metal in DME or THF. The perylene ligand was transferred to a samarium metal center using a metathesis strategy, yielding a complex SmI(Per)(THF)4. In the resulting compound, samarium remains divalent, while perylene is in the form of a radical anion, which is confirmed by spectroscopic methods and quantum chemical calculations.

Ditopic di-o-quinone with a resorcinol bridge exhibits the ability to self-assemble in a reaction with copper, giving a cage-like binuclear complex that, due to the cofacially placed metal ions, is capable of encapsulation of different solvent molecules as guest ligands. Notably, the geometry of the internal cavity of this complex adjusts depending on the coordinating properties of the encapsulated molecule (mono- or bidentate). A feature of this species is that the cage-forming units are copper(II) bis-semiquinonate moieties, capable of undergoing ligand-centered redox transformations. Electrochemical and EPR spectroscopy studies showed that there is a channel for intramolecular electronic exchange interactions between the redox centres of the molecule.

The possibility of the application of nitronyl-nitroxide ligand (NIT) as a spin label for the study of the composition of transition metals complexes with M-NIT bonds by EPR spectroscopy was explored using PCP-pincer complexes of Pd and Ni as examples.

Two novel dicarbonyl-semiquinonato rhodium complexes were synthesized and studied. Complexes are analogues of (CO)(2)Rh(3,6-DBSQ) (3,6-DBSQ-3,6-di-tert-butyl-o-benzosemiquinone) which thread-like crystals can bend reversibly under light or heat activation (G.A. Abakumov, V.I. Nevodchikov, Dokl. Acad. Nauk SSSR 1982, 266, 1407-1410). Complexes differ from (CO)(2)Rh(3,6-DBSQ) by substituents in 3,6-positions of quinonato ring (cyclohexyl (1) and isopropyl (2) instead of tert-butyl). Single crystal structural study indicates that both complexes are the derivatives of Rh(I) with o-semiquinonato anion-radical. Molecules form pairs due the short contacts in contrast to (CO)(2)Rh(3,6-DBSQ) and other similar compounds which form the endless alternated chains with direct Rh-Rh bond. At that, complex 1 molecules form isolated pairs, whereas molecules of 2 can be united in the chain. Both compounds 1 and 2 have the array of intensive bands in IR spectrum in the region 1350 cm(-1) which is closer to bond stretch vibrations of C-O ordinary bond but not sesquilateral. EPR of solutions of complexes indicates presence of monomeric complex molecules where the single unpaired electron is localized in o-semiquinonato ligand. The drop of EPR signal intensity with cooling of solutions of 1 and 2 evidence that the association process takes place. (C) 2021 Elsevier Ltd. All rights reserved.

Especially grown crystals (elongated plates) of the complex (1,10-phen)Co(3,6-DBSQ)(2) (1) reversibly elastically bend under laser excitation (532 or 808 nm) and/or heating in the temperature interval similar to 242-265 K (1,10-phen = 1,10-phenanthroline, 3,6-DBSQ = anion-radical and 3,6-DBCat = dianion of 3,6-di-tert-butyl-o-benzoquinone). The abrupt interconversion of valence tautomers is observed in this temperature range: (phen)Co(3,6-DBCat)(3,6-DBSQ) (sic) (phen)Co-(3,6-DBSQ)(2). Solving the problem of design of photo- (thermo-) actuators with preset parameters, the series of solid solutions of general formula (phen)(x)(bpy)(1-x)Co(3,6-DBSQ)(2) was obtained and crystallized as thin elongated plates. Crystals of each solid solution demonstrate the maximal photomechanical response (bending) at a temperature close to its own valence tautomeric (VT) transition temperature. On the other hand, the VT transition temperature depends on the composition of the solid solution. So, by setting the composition of the solid solution, one can set the temperature of the photomechanical response. It is the first example of temperature-manageable photomechanical properties.

The heterospin copper(II) complex, ((pyridin-2-ylmethylene)-4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl)-3,6-di- tert -butylcatecholatocopper(II) ( I ), is synthesized and characterized by IR spectroscopy, magnetochemistry, EPR, and X-ray diffraction analysis. The one-electron oxidation of complex I by AgBF 4 affords the biradical copper(I) complex: bis[((pyridin-2-ylmethylene)-4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl)]copper(I) ( II ). An analysis of the parameters of isotropic EPR spectra of complexes I and II indicates that they are biradicals with the fast ( I ) and intermediate ( II ) exchange interaction between the radical centers.