Gelatin Matrix as Functional Biomaterial for Immobilization of Nanoparticles of Metal-Containing Compounds

The data concerning the synthesis and physicochemical characteristics of specific functional biomaterials-biopolymer-immobilized matrix systems based on gelatin as an array and chemical compounds, which include atoms of various metal elements-are systematized and discussed. The features of this biopolymer which determine the specific properties of the immobilized matrix systems formed by it and their reactivity, are noted. Data on gelatin-immobilized systems in which immobilized substances are elemental metals and coordination compounds formed as a result of redox processes, nucleophilic/electrophilic substitution reactions, and self-assembly (template synthesis), are presented. The possibilities of the practical use of metal-containing gelatin-immobilized systems are promising for the future; in particular, their potential in medicine and pharmacology as a vehicle for "targeted" drug delivery to various internal organs/tissues of the body, and, also, as potential biosensors is noted.

Series of Fluorinated Benzimidazole-Substituted Nitronyl Nitroxides: Synthesis, Structure, Acidity, Redox Properties, and Magnetostructural Correlations

A special series of nitronyl nitroxides was synthesized: 2-(benzimidazol-2'-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyls mono-, di-, tri-, or tetrafluorinated on the benzene ring. The structure of all paramagnets was unambiguously confirmed by single-crystal X-ray diffraction. It was found that in crystals, the radicals are assembled into chains due to intermolecular H-bonds between the benzimidazole moiety (H-bond donor) and the nitronyl nitroxide group or benzimidazole ring (H-bond acceptor). The magnetic properties of nitronyl nitroxides depend on the type of binding of radicals by H-bonds. The magnetic motif of 4-fluoro-, 5-fluoro-, 4,6-difluoro-, 4,5,6-trifluoro-, 4,5,7-trifluoro-, and 4,5,6,7-tetrafluoro-derivatives, as well as the nonfluorinated compound, consists of ferromagnetic chains (J/k_B ≈ 20-40 K) formed by the McConnell type I mechanism. In the 5,6-difluoro- and 4,5-difluoro-derivatives, the distances between the paramagnetic centers are large, as a result of which the exchange interactions are weak. According to cyclic voltammetry, paramagnets are oxidized reversibly, while their reduction is a quasi-reversible electron transfer (EC mechanism); experimental redox potentials of radicals correlate well with the calculated values. Quantum chemical assessment of the acidity of benzimidazolyl-substituted nitronyl nitroxides revealed that the introduction of fluorine atoms into the benzene ring enhances the acidity of the paramagnets by more than 5 orders of magnitude.

Recent advancements on hyperthermia driven controlled drug delivery from nanotherapeutics

Previous reviews of the works on magnetic nanoparticles for hyperthermia induced treatment concentrated mostly on magnetic fluid hyperthermia (MFH) employing monometallic/metal oxide nanocomposites. In the literature, the word "hyperthermia" was also limited to the use of heat for medicinal purposes. A number of publications have recently been published demonstrating that magnetic nanoparticle-based hyperthermia may produce restricted high temperatures, resulting in the release of medicines that are either connected to the magnetic nanoparticles or encased in polymer matrices. In this debate, we propose broadening the concept of "hyperthermia" to encompass temperature-based treatment as well as magnetically controlled medication delivery. The review also addresses core-shell magnetic nanomaterials, particularly nanoshells made by stacked assembly, for the use of hyperthermia-based treatment and precise administration of drugs. The primary objective of this review article is to demonstrate how the combination of hyperthermia-induced therapy and 'on demand' drug release models may lead to effective applications in personalized medicine.

Syntheses, structures, and magnetic properties of the lanthanide complexes of imidazole-substituted nitronyl nitroxide biradicals

Two new bis-bidentate imidazole-substituted nitronyl nitroxide biradicals, BNITIm-C2 (BNITIm-C2 = 1,1'-(1,2-ethanediyl)bis(1H-imidazole-2-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-oxide)) and BNITIm-C4 (BNITIm-C4 = 1,1'-(1,4-butanediyl)bis(1H-imidazole-2-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-oxide)), and two series of lanthanide complexes, namely [(BNITIm-C2)Ln(NO₃)₃](MeOH) (Ln = Gd (1Gd) and Tb (2Tb)), (BNITIm-C2)Dy(NO₃)₃ (3Dy) and (BNITIm-C4)[Ln(hfac)₃]₂(C₇H₈)₂ (Ln = Gd (4Gd), Tb (5Tb) and Dy (6Dy), hfac = hexafluoroacetylacetonate), have been prepared and characterized structurally and magnetically. Single crystal X-ray crystallographic analyses revealed that complexes 1Gd-3Dy exhibit 1D chain structures where the Ln(NO₃)₃ units are bridged by the BNITIm-C2 bis-bidentate biradical, while complexes 4Gd-6Dy exhibit binuclear structures with two Ln(hfac)₃ units bridged by the BNITIm-C4 biradical. The bulky hfac anions prohibit the further coordination of Ln^III to another NIT ligand and the formation of a similar 1D chain structure. Due to the very long intra- and intermolecular distances of the spin centers, complexes 1Gd-3Dy can be magnetically regarded as an isolated 2p-4f-2p tri-spin system while complex 4Gd-6Dy can be regarded as an isolated 2p-4f bi-spin system. Magnetic analyses on the two Gd^III compounds revealed the ferromagnetic Gd^III-NIT interactions and antiferromagnetic NIT-NIT interactions through the Gd^III ion in 1Gd. Alternating-current (ac) magnetic susceptibility investigations revealed that complex 5Tb exhibits the typical SMM behavior under a zero dc field while complex 6Dy was proved to be a field-induced SMM. Ab initio calculations were performed on complexes 2Tb and 5Tb to understand their magnetic anisotropy together with their different magnetic dynamics.

The heterospin cobalt complexes: peculiarities of high-resolution NMR spectra

The high-resolution ¹H and ¹³C NMR spectra (CHCl₃ solution) of sterically non-rigid heterospin complexes CoL₂, CoL₂-dipy, and CoL₂-phen (where L is 4-(3',3',3'-trifluoro-2'-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-1-oxyl) have been studied. The specific of the NMR phenomenon in paramagnetic systems is briefly analyzed. It is shown that the NMR spectra modified by hyperfine coupling can be successfully employed for investigation of the complexation processes. In accordance with the common protocols, the ¹H and ¹³C NMR signals are assigned using the information on ¹³С - ¹Н spin-spin coupling. In addition, the preliminarily recorded ¹H and ¹³C NMR spectra of radical L are also used in the work. The temperature dependences of ¹H and ¹³C paramagnetic shifts in the complexes under study have been obtained. A fundamental feature of these dependences is that they obey to the Curie law in a fairly wide temperature range (up to 100 °C). This observation can be used to control intramolecular processes of sterically nonrigid heterosystems in solutions.

Pressure and temperature dependences of the canting angle and increase in the magnetic ordering temperature, Tc(P), for the weak ferromagnet Li+[TCNE]˙- (TCNE = tetracyanoethylene)

The hydrostatic pressure dependence of the magnetic ordering temperature, T_c(P), for the interpenetrating, diamondoid lattice-structured, weak ferromagnet (= canted antiferromagnet) Li⁺[TCNE]˙^- (TCNE = tetracyanoethylene) reversibly increases from 20.9 to 23.4 K at 9.73 kbar, an increase of 12% with a rate of increase, dT_c/dP, of 0.27 K kbar^-1. The 5 T magnetization increased by 672% from 186 emu Oe mol^-1 at ambient pressure to an average of 1440 emuOe mol^-1 upon application of pressure. The remanent magnetization initially increases 30% from 10.8 to 14.0 emuOe mol^-1 from ambient to 0.06 kbar, and increases further by 6% to a maximum of 14.8 emuOe mol^-1 at 0.56 kbar before declining by 22% to 11.5 emuOe mol^-1 at 9.73 kbar. The pressure-dependent coercive field, H_cr(P), initially decreases by 42% from 31.1 Oe at ambient pressure to 18 Oe at 0.06 kbar, then increases to 52 Oe at 9.73 kbar. The canting angle, α, increases by 28% from 0.52° to 0.66° at 0.06 kbar, then decreases by 23% to 0.51° at 9.73 kbar, as well as increases by 2% from 0.536° to 0.548° from 1.8 to 2.5 K, before decreasing by 79% to 0.117° at 19 K. The interlattice interactions are attributed to be the primary exchange mechanism. Thus, α(T) and α(P) have similar dependencies that are attributed to a competition between an increase and a decrease in the intra- and interlayer C⋯N interlattice separations as the temperature and pressure increases.

Low temperature structures and magnetic interactions in the organic-based ferromagnetic and metamagnetic polymorphs of decamethylferrocenium 7,7,8,8-tetracyano-p-quinodimethanide, [FeCp*2]˙+[TCNQ]˙. Dalton Trans 2021;50:11228-11242. [PMID: 34338700 DOI: 10.1039/d1dt02106k]

To identify the genesis of the differing magnetic behaviors for the ferro- (FO) and metamagnetic (MM) polymorphs of [FeCp*₂][TCNQ] (Cp* = pentamethylcyclopentadienide; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) the low temperature (18 ± 1 K) structures of each polymorph were determined from high-resolution synchrotron powder diffraction data. Each polymorph possesses chains of alternating S = 1/2 [FeCp*₂]˙⁺ cations and S = 1/2 [TCNQ]˙⁺, but with differing relative orientations. These as well as an additional paramagnetic polymorph do not thermally interconvert. In addition, the room and low (<70 ± 10 K) temperature structures of the MM polymorph, MM_RT and MM_LT, respectively, differ from that previously reported at 167 K (-106 °C) MM structure, and no evidence of either phase transition was previously noted even from the magnetic data. This transition temperature and enthalpy of this phase transition for MM_RT⇌MM was determined to be 226.5 ± 0.4 K (-46.7 ± 0.4 °C) and 0.68 ± 0.04 kJ mol^-1 upon warming, respectively, from differential calorimetry studies (DSC). All three MM phases are triclinic (P1[combining macron]) with the room temperature phase having a doubled unit cell relative to the other two. The lower temperature phase transition involves a small rearrangement of the molecular ions and shift in lattice parameters. These three MM and FO polymorphs have been characterized and form extended 1-D chains with alternating S = 1/2 [FeCp*₂]˙⁺ cations, and S = 1/2 [TCNQ]˙^- anions, whereas the fifth, paramagnetic (P) polymorph possesses S = 0 π-[TCNQ]₂^2- dimers. At 18 ± 1 K the intrachain FeFe separations are 10.738(2) and 10.439(3) Å for the FO and MM_LT polymorphs, respectively. The key structural differences between FO and MM_LT at 18 ± 1 K are the 10% shorter interchain NN and the 2.8% shorter intrachain FeFe separation present for MM_LT. Computational analysis of all nearest-neighbor spin couplings for the 18 K structures of FO and MM_LT indicates that the intrachain [FeCp*₂]˙⁺[TCNQ]˙^- spin couplings (H = -2S_i·S_j) are the strongest (4.95 and 6.5 cm^-1 for FO and MM_LT, respectively), as previously hypothesized, and are ferromagnetic due to their S = 1/2 spins residing in orthogonal orbitals. The change in relative [TCNQ]˙^-[TCNQ]˙^- orientations leads to a computed change from the ferromagnetic interaction (0.2 cm^-1) for FO to an antiferromagnetic interaction (-0.1 cm^-1) for MM_LT in accord with its observed antiferromagnetic ground state. Hence, the magnetic ground state cannot be solely described by the dominant magnetic interactions.

Cracking under Internal Pressure: Photodynamic Behavior of Vinyl Azide Crystals through N2 Release

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N₂. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of 1a delaminate and release gaseous N₂ indiscriminately under paraffin oil, the crystals of 1b and 1c visibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N₂. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of 1b and 1c where elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.

From spin-labelled fused polyaromatic compounds to magnetically active graphene nanostructures

Molecular design of magnetically active graphene nanoscale structures is an emerging field of research. The key goal of this research is to produce graphene nanoribbons and graphene quantum dots with specified electronic, optical and magnetic properties. The review considers methods for the synthesis of spin-labelled polycyclic aromatic hydrocarbons, which are homologous precursors of graphene nanostructures, and discusses the advances and prospects of the design of magnetically active graphene materials.

The bibliography includes 134 references.

A nitronyl nitroxide and its two 1D chain Cu–Tb complexes: synthesis, structures, and magnetic properties

A new nitronyl nitroxide, namely NIT-Ph-p-OCH₂trz (1), and two types of one-chain Cu–Tb complexes, namely [TbCu(hfac)₅NIT-Ph-p-OCH₂trz·0.5C₆H₁₄]_n (2a) and [LnCu(hfac)₅NIT-Ph-p-OCH₂trz]_n (2b) (NIT-Ph-p-OCH₂trz = 2-(4-((1H-1,2,4-triazol-1-yl)methoxy)phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate), have been successfully synthesized simultaneously through reacting nitronyl nitroxide radical NIT-Ph-p-OCH₂trz with Cu(hfac)₂ and Ln(hfac)₃, and the molecular structures have been elucidated via single-crystal X-ray structural analysis. 2a features a ‘ladder-like’ chain structure, while 2b displays a linear chain structure built up by Ln(hfac)₃ units bridged with the NO groups of radical ligands. The additional Cu(ii) ions are coordinated to the nitrogen atoms of the triazole units. Nonzero out-of-phase signals are observed for the Tb derivatives (2a and 2b) and they exhibit frequency-dependent out-of-phase signals indicating a single-chain magnet behavior.

A new nitronyl nitroxide and two types of one-chain Cu–Tb complexes have been successfully synthesized, and the molecular structures have been elucidated via single-crystal X-ray structural analysis.

Electrophilic substitution in the d-metal hexacyanoferrate(II) gelatin-immobilized matrix systems

Data of electrophilic substitution processes proceeding into the d-metal hexacyanoferrate(II) gelatin-immobilized matrix systems when they are in contact with aqueous solutions of chlorides of d-elements have been systematized and generalized. The bibliography includes 94 references.

Ferromagnetic Coupling in the Heterospin Bis-Catecholato-Manganese(IV) Complex with Pyridine Substituted by Nitronyl-nitroxide

A new bis(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py ligands was synthesized and characterized [4-NIT-Py = pyridine substituted at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination core of the metal and in the chelate cycles that are representative of the charge distribution between the metal and ligands displayed a Mn(IV)(Cat^2-)₂ charge distribution. Variable-temperature magnetic susceptibility measurements detected intramolecular ferromagnetic coupling between the Mn(IV) S = ³/₂ spins and spins of nitronyl-nitroxyls and intermolecular ferromagnetic interactions of spins of adjacent nitronyl-nitroxide fragments in a chain of molecules at low temperatures. The last phenomenon is revealed by short contacts between nitronyl-nitroxide radicals of adjacent complex molecules.

Synthesis and magnetic and cytotoxic properties of copper(ii) halide complexes with 1,2,4-triazolo[1,5-a] benzimidazoles

Coordination compounds based on copper(ii) halides with 4H-1,2,4-triazolo[1,5-a]benzimidazole (L) and its derivatives with the compositions [CuL₂Hal₂]·nH₂O.

Characterization of Tetracyanopyridine (TCNPy)-Based Magnets: V[TCNPy]2 ⋅z (CH2 Cl2 ) (Tc =111 K) and V[TCNPy]3 ⋅z (CH2 Cl2 ) (Tc =90 K)

The reaction of 2,3,5,6-tetracyanopyridine (TCNPy) with V(CO)6 in CH2 Cl2 forms new organic-based magnets of V[TCNPy]x ⋅z (CH2 Cl2 ) (x=2, 3) composition. Analysis of the IR spectra suggests that the TCNPy is reduced and coordinated to V(II) sites through the nitriles. V[TCNPy]x order as ferrimagnets with 111 and 90 K Tc values for V[TCNPy]2 and V[TCNPy]3 , respectively. Their respective remanent magnetizations and coercive fields are 1260 and 250 emuOe mol(-1) and 9 and 6 Oe at 5 K, and they exhibit some spin-glass behavior.

Hexacyanobutadienide-Based Frustrated and Weak Ferrimagnets: M(HCBD)2·zCH2Cl2 (M = V, Fe)

Hexacyanobutadiene (HCBD) and M(CO)x (M = V, x = 6; Fe, x = 5) react in CH2Cl2 to form new organic-based magnets of M[HCBD]2·z(CH2Cl2) composition. Analysis of the IR spectrum [M = V: ν(CN) 2193 and 2116 cm(-1) (fwhh ∼400 cm(-1)); Fe: 2196 and 2145 (fwhh ∼150 cm(-1))] suggests that HCBD is reduced to the radical anion, [HCBD](•-), and the broadness suggests multiple and variable nitriles sites are coordinated to the V(II), leading to a complex mixture of magnetic couplings and behaviors that deviate from paramagnetic behavior below ∼150 K, and a frustrated magnet with Tc ≈ 9 K is observed for V[HCBD]2, the first cyanocarbon-based frustrated magnet. Fe[HCBD]2 behaves as a weak ferromagnet (canted antiferromagnet) with some spin glass behavior with a 10 K Tc.

Supramolecular aggregates of single-molecule magnets: exchange-biased quantum tunneling of magnetization in a rectangular [Mn3]4 tetramer

Exchange-biased QTM within a magnetically-supramolecular tetramer of Mn₃ single-molecule magnets with spin S = 6 has been analyzed.

The syntheses and properties of four magnetically-supramolecular oligomers of triangular Mn₃ units are reported: dimeric [Mn₆O₂(O₂CMe)₈(CH₃OH)₂(pdpd)₂] (3) and [Mn₆O₂(O₂CMe)₈(py)₂(pdpd)₂](ClO₄)₂ (4), and tetrameric [Mn₁₂O₄(O₂CR)₁₂(pdpd)₆](ClO₄)₄ (R = Me (5), ^tBu (6)). They were all obtained employing 3-phenyl-1,5-di(pyridin-2-yl)pentane-1,5-dione dioxime (pdpdH₂), either in direct synthesis reactions involving oxidation of Mn^II salts or in metathesis reactions with the preformed complex [Mn₃O(O₂CMe)₆(py)₃](ClO₄) (1); complex 6 was then obtained by carboxylate substitution on complex 5. Complexes 3 and 4 contain two [MnIII2Mn^II(μ₃-O)]⁶⁺ and [MnIII3(μ₃-O)]⁷⁺ units, respectively, linked by two pdpd^2– groups. Complexes 5 and 6 contain four [MnIII3(μ₃-O)]⁷⁺ units linked by six pdpd^2– groups into a rectangular tetramer [MnIII3]₄. Solid-state dc magnetic susceptibility studies showed that the Mn₃ subunits in 3 and 4 have a ground-state spin of S = 3/2 and S = 2, respectively, while the Mn₃ subunits in 5 and 6 possess an S = 6 ground state. Complexes 5 and 6 exhibit frequency-dependent out-of-phase (χ′′_M) ac susceptibility signals indicating 5 and 6 to be tetramers of Mn₃ single-molecule magnets (SMMs). High-frequency EPR studies of a microcrystalline powder sample of 5·2CH₂Cl₂ provided precise spin Hamiltonian parameters of D = –0.33 cm^–1, |E| = 0.03 cm^–1, B04 = –8.0 × 10^–5 cm^–1, and g = 2.0. Magnetization vs. dc field sweeps on a single crystal of 5·xCH₂Cl₂ gave hysteresis loops below 1 K that exhibit exchange-biased quantum tunneling of magnetization (QTM) steps with a bias field of 0.19 T. Simulation of the loops determined that each Mn₃ unit is exchange-coupled to the two neighbors linked to it by the pdpd^2– linkers, with an antiferromagnetic inter-Mn₃ exchange interaction of J/k_B = –0.011 K (Ĥ = –2Jŝ_i·ŝ_j convention). The work demonstrates a rational approach to synthesizing magnetically-supramolecular aggregates of SMMs as potential multi-qubit systems for quantum computing.