Half-Sandwich Rhodium Complexes with Releasable N-Donor Monodentate Ligands: Solution Chemical Properties and the Possibility for Acidosis Activation

Cancer chemotherapeutics usually have serious side effects. Targeting the special properties of cancer and activation of the anticancer drug in the tumor microenvironment in situ may decrease the intensity of the side effects and improve the efficacy of therapy. In this study, half-sandwich Rh complexes are introduced, which may be activated at the acidic, extracellular pH of the tumor tissue. The synthesis and aqueous stability of mixed-ligand complexes with a general formula of [Rh(η5-Cp*)(N,N/O)(N)]2+/+ are reported, where (N,N/O) indicates bidentate 8-quinolate, ethylenediamine and 1,10-phenanthroline and (N) represents the releasable monodentate ligand with a nitrogen donor atom. UV-visible spectrophotometry, 1H NMR, and pH-potentiometry were used to determine the protonation constants of the monodentate ligands, the proton dissociation constants of the coordinated water molecules in the aqua complexes, and the formation constants of the mixed-ligand complexes. The obtained data were compared to those of the analogous Ru(η6-p-cymene) complexes. The developed mixed-ligand complexes were tested in drug-sensitive and resistant colon cancer cell lines (Colo205 and Colo320, respectively) and in four bacterial strains (Gram-positive and Gram-negative, drug-sensitive, and resistant) at different pH values (5–8). The mixed-ligand complexes with 1-methylimidazole displayed sufficient stability at pH 7.4, and their activation was found in cancer cells with decreasing pH; moreover, the mixed-ligand complexes demonstrated antimicrobial activity in Gram-positive and Gram-negative bacteria, including the resistant MRSA strain. This study proved the viability of incorporating releasable monodentate ligands into mixed-ligand half-sandwich complexes, which is supported by the biological assays

Half-Sandwich Rhodium Complexes with Releasable N-Donor Monodentate Ligands: Solution Chemical Properties and the Possibility for Acidosis Activation

Cancer chemotherapeutics usually have serious side effects. Targeting the special properties of cancer and activation of the anticancer drug in the tumor microenvironment in situ may decrease the intensity of the side effects and improve the efficacy of therapy. In this study, half-sandwich Rh complexes are introduced, which may be activated at the acidic, extracellular pH of the tumor tissue. The synthesis and aqueous stability of mixed-ligand complexes with a general formula of [Rh(η5-Cp*)(N,N/O)(N)]2+/+ are reported, where (N,N/O) indicates bidentate 8-quinolate, ethylenediamine and 1,10-phenanthroline and (N) represents the releasable monodentate ligand with a nitrogen donor atom. UV-visible spectrophotometry, 1H NMR, and pH-potentiometry were used to determine the protonation constants of the monodentate ligands, the proton dissociation constants of the coordinated water molecules in the aqua complexes, and the formation constants of the mixed-ligand complexes. The obtained data were compared to those of the analogous Ru(η6-p-cymene) complexes. The developed mixed-ligand complexes were tested in drug-sensitive and resistant colon cancer cell lines (Colo205 and Colo320, respectively) and in four bacterial strains (Gram-positive and Gram-negative, drug-sensitive, and resistant) at different pH values (5–8). The mixed-ligand complexes with 1-methylimidazole displayed sufficient stability at pH 7.4, and their activation was found in cancer cells with decreasing pH; moreover, the mixed-ligand complexes demonstrated antimicrobial activity in Gram-positive and Gram-negative bacteria, including the resistant MRSA strain. This study proved the viability of incorporating releasable monodentate ligands into mixed-ligand half-sandwich complexes, which is supported by the biological assays

Retain strength, gain ductility: tough and transparent nanopapers by mercerisation

Nanocellulose papers offer high tensile strength and modulus but suffer from drawbacks such as their brittle nature. We show that mercerisation of cellulose nanopapers in strong alkaline media for 2 min to 24 h results in the (partial) transformation of native cellulose I into the more ductile cellulose II allomorph. The strain to failure of mercerised nanopapers tripled compared to the original nanopapers while retaining their tensile strength in excess of 100 MPa at the expense of a slight drop in modulus resulting in a significant increase in toughness (total work of fracture). An additional advantage of mercerisation is a reduction in porosity of the nanopapers and increased transparency.Validerad;2024;Nivå 2;2024-04-05 (signyg);Funder: Institute of Materials Chemistry (371300);Full text license: CC BY</p

Room Temperature Synthesis of Cu-BTC Coordination Polymer and Metal-Organic Framework by pH Control

Synthesis of crystalline materials is crucial in the field ofcoordination chemistry. In the present work, the reactionbetween the copper and benzene-1,3,5-tricarboxylic acid(BTC) ligand is controlled by adjusting the pH of thereaction mixture to synthesize two crystalline structures:metal-organic framework HKUST-1 and one-dimensionalcoordination polymer Cu(BTC).3H2O. Single crystals of bothstructures are studied by multi-laser Raman spectroscopy.It is found that both crystals exhibit photoluminescence.Also, the transformation of HKUST-1 into Cu(BTC).3H2O isdemonstrated. This work provides impetus for researchersto synthesize large metal-organic crystals.</div

Racemic and Meso Crystal Structures of an Axial-Chiral Spirobi-(dinaphthoazepin)ium Salt: Emergence of an S4-Symmetric Molecule

To date, only a few instances of S4-symmetric organic molecules exist. In principle, spirobi-(dinaphthoazepin)ium cations can achieve this highly symmetric point group. Heating racemic 2,2′-bis(bromomethyl)-1,1′binaphthyl with aqueous ammonia afforded a mixture of rac- and meso-3,3′,5,5′-tetrahydro-4,4′-spirobi[dinaphtho[2,1-c:1′,2′-e]azepin]-4-ium bromide which was separated by fractional crystallisation. Both stereoisomers were characterised spectroscopically, and their crystal structures were determined and compared. The rac crystal structure differs significantly from the known enantiopure one. The meso molecules display a near-perfect S4 symmetry. Upon treatment with KOtBu, both isomers undergo Stevens rearrangement

A field-induced exchange flip in a spin linear trimer in a coordination polymer of cobalt and melamine

A coordination polymer of linear trimeric cobalt and melamine has been synthesized. The magnetic isotherms of violet coloured crystals as long as 400 μm show a field-induced transition in an external field of about 2 T at temperatures below 2 K. It is addressed that by assuming the coexistent positive and negative exchange between the nearest-neighbour spins in the linear trimer, this metamagnetic transition can be understood as a transition from antiferromagnetic to ferromagnetic exchange within each trimeric spin cluster without considering long-range magnetic ordering. Although weak inter-cluster or inter-chain exchange to yield a long-range magnetic order is not excluded as another possible and often attributed origin of metamagnetism in low-dimensional spin systems, the present study demonstrates the significance of the exchange flip within each cluster in clustered spin networks. This paves the way towards the realization of stable, yet switchable states of a spin trimer in the realm of coordination chemistry

Highly luminescent TCNQ in melamine

Optical properties of molecules change drastically as results of interactions with surrounding environments as observed in solutions, clusters and aggrergates. Here we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Coloured single crystals are synthesized by slow evaporation of a solution of melamine and TCNQ in water and tetrahydrofuran. Single crystal X-ray diffraction reveals the lattice structure of pure melamine, meaning that the colour is of impurities. Both mass spectrometry and UV-Vis spectroscopy combined with density-functional theory calculations elucidate that the impurity species are neutral TCNQ and its oxidation product, dicyano-$p$-toluoyl cyanide anion (DCTC$^-$), whose concentrations in a melamine crystal can be controlled by adjusting the molar ratio between melamine and TCNQ in the precursor solution. Fluorescence exciation-emission wavelength mappings on the precursor solutions illustrate dominant emissions from DCTC$^-$ while the emission from TCNQ is quenched by the resonance energy transfer to DCTC$^-$. On the contrary, TCNQ in crystalline melamine is a bright fluorophore whose emission wavelength centered at 450 nm and slow fluorescence lifetimes of about 2 ns. Our method of encapsulating molecules into transparent melamine would make many other molecules fluorescencent in solids

Metamagnetism in a coordination polymer built of trimeric cobalt units and melamine

A coordination polymer of linear trimeric cobalt units and melamine has been synthesized. The magnetic isotherms of violet coloured crystals as long as 400 μm show a field-induced transition in an external field of about 2 T at temperatures approximately below 2 K. It is addressed that by assuming the coexistent positive and negative exchange between the nearest-neighbour spins in the linear trimer, this metamagnetism can be interpreted as a transition from antiferromagnetic to ferromagnetic exchange within each trimeric spin cluster. Although weak inter-cluster or inter-chain exchange to yield a long-range magnetic order is another possible and often attributed origin of metamagnetism in low-dimensional spin systems, this study demonstrates the significance of the exchange flip within each cluster in clustered spin networks

Crystal Engineering with Copper and Melamine

Coordination complex and polymer are central in inorganic and material chemistry as a variety of both metal centers and coordination geometries lead to a diverse range of interesting properties. Here, size and structure control of gems-like quality monocrystals are demonstrated at room temperature. From the same set of precursors, but the copper-to-melamine molar ratio is adjusted to synthesize either a novel coordination complex of dinuclear copper and melamine (Cu2M1) or a barely-studied coordination polymer of zigzag copper-chlorine chains (Cu4M1). Crystals of the former are dark green and squared with the size up to 350 µm across. The latter is light green and octagonal as large as 5 mm across. The magnetic properties of both crystals reflect their low-dimensional arrangements of copper. The magnetic susceptibility of Cu2M1 is well modelled with a spin-1/2 dimer and that of Cu4M1 with a spin-1/2 one-dimensional Ising chain. Controlled synthesis of such quality magnetic crystals is a prerequisite for various magnetic and magneto-optical applications<br /

A novel molecular assembly of cobalt-sulfite coordination polymer and melamine: a manifestation of magnetic anisotropy

A novel molecular assembly of cobalt-sulfite coordination polymer and melamine is synthesized under acidic conditions. Bar-shaped pink monocrystals as long as 1 mm are found to align along magnetic field lines at the proximity of a strong magnet. Magnetometry shows no hysteresis at temperatures down to 2K, but magnetic anisotropy and antiferromagnetic coupling. X-ray diffraction on a single crystal reveals that the cobalt-sulfite chains are along the shortest lattice vector or the crystal\u27s long axis. The crystal alignment along the magnetic flux can be attributed to single-ion anisotropy that results in longitudinal antiferromagnetic coupling along the chain. Both structurally and magnetically isotropic crystals of metal-organic hybrid materials can be highly useful as elemental components in magneto-optics