Spin‐crossover complexes with multistep transitions attract much attention due to their potential applications as multi‐switches and for data storage. A four‐step spin crossover is observed in the ...new iron(II)‐based cyanometallic guest‐free framework compound Fe(2‐ethoxypyrazine)2{Ag(CN)2}2 during the transition from the low‐spin to the high‐spin state. A reverse process occurs in three steps. Crystallographic studies reveal an associated stepwise evolution of the crystal structures. Multiple transitions in the reported complex originate from distinct FeII sites which exist due to the packing of the ligand with a bulky substituent.
A new guest‐free Hofmann clathrate analogue Fe(2‐ethoxypyrazine)2{Ag(CN)2}2 which undergoes a four‐step spin crossover during the transition from the low‐spin to the high‐spin state is reported. At the first step 1/3 of centers become high spin, at the second step another 1/3 of centres become high spin, at the third step spin mixed crystallographic centres are observed, and after the fourth step all centers are high spin.
A series of isoreticular lanthanide–organic frameworks derived from a lengthy dicarboxylate ligand with a terphenyl core have been synthesized and characterized. Evaluation of their luminescence ...showed that the Tb3+-MOF has an expected emission quantum yield of 98%.
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•Solvothermal synthesis of lanthanide–organic frameworks is reported.•Single crystal X-ray structures were established for six coordination polymers.•These isoreticular networks include nitrate, water and DMF in their structure.•Luminescent properties of these MOFs have been investigated.•Tb(III)-based MOF has an expected emission quantum yield of 98%.
A series of 3D metal–organic frameworks derived from 2′,3′,5′,6′-tetramethyl-1,1′:4′,1′′-terphenyl-4,4′′-dicarboxylic acid (H2L) as organic linker and various lanthanides have been prepared. The resulting coordination polymers Ln3L4(NO3)(DMF)x(H2O)n (where x = 2 or 3) were characterized by elemental analysis, thermogravimetric investigations, IR and TG-FTIR spectroscopy, as well as powder X-ray diffraction measurements. The crystal structure for six of these isostructural networks based on La(III), Ce(III), Nd(III), Sm(III), Tb(III) and Dy(III) was established using single crystal X-ray crystallography. As an example, the asymmetric part of La3L4(NO3)(DMF)3(H2O)n consists of two deprotonated ligand molecules L2- and two La(III) ions, one of them occupying a general position with full site occupancy, while the other one has a fractional occupancy of 0.5. Investigation of the luminescence of these coordination polymers showed that compounds containing La3+, Nd3+ and Gd3+ possess only the emission associated with the anion of the organic ligand (L2-), polymers containing Eu3+ and Tb3+ show pure metal-centered radiation, while networks containing Dy3+ and Sm3+ display dual metal- and ligand-centered luminescence. The organic linker acts as a good antenna for Tb3+, Eu3+, Dy3+ and Sm3+ ions.
Examination of the potential of the title ligand for the generation of coordination compounds with transition metal ions led to the isolation of novel Cd(II)-based networks and Cu(II)-based ...complexes. Cd(II)-containing networks derived from this ligand that also incorporate co-ligands (4,4′-bipyridine or 4,4′-azopyridine) in their structure have been described for the first time.
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The straightforward and facile synthetic approaches towards four coordination polymers, {CdL(H2O)·0.5H2O}n, {Cd2L2(H2O)2(4,4′-bipy)·4H2O}n, {Cd2L2(H2O)2(4,4′-azpy)·3H2O}n and {CoL(H2O)3·2.5H2O}n (4,4′-bipy = 4,4′-bipyridine; 4,4′-azpy = 4,4′-azopyridine), based on the polydentate ligand 1-(4-carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid (LH2) and Cd(II) and Co(II) ions are reported. In addition, two mononuclear complexes, Cu(HL)2(DMA) and Cu(HL)2(H2O)2, derived from the same ligand and the Cu(II) ion have been prepared. The coordination compounds have been characterized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis. Single crystal X-ray structures for each of these coordination compounds have been established. The specific surface of the 3D Cd(II)- and Co(II)-derived coordination polymers, determined through nitrogen adsorption, is negligible (SBET < 25 m2/g).
Four novel ditopic ligands that have a pyrazole ring in their central unit and are useful for the generation of coordination polymers have been synthesized. Two of these ditopic ligands present two ...carboxylate functions as coordinating groups, while the other two are hybrid ligands having only one carboxylate function and either tetrazolate or imidazole as the remaining coordination site. The ligands have been obtained through a multi-step reaction sequence that begins with the Claisen condensation of either 4-acetylbenzonitrile or 4-(1
H
-imidazol-1-yl)acetophenone with diethyl oxalate and has the Knorr pyrazole ring closure as its key step. Subsequently, the tetrazolate in one of the ligands is constructed through a 3 + 2 cycloaddition of azide anion to the cyano group, while hydrolysis of the ester and the cyano substituents generates the carboxylate function(s). The structure of the intermediates and of the target ligands has been investigated by solution NMR, special attention being given to keto–enol and pyrazole tautomerism when present. The structure of two ligands and a key intermediate has also been established by single-crystal X-ray diffraction.
Polymers play a crucial role in multiple industries; however, surface modification is necessary for certain applications. Exposure to non-thermal plasma provides a viable and environmentally ...beneficial option. Fused deposition molding utilizes biodegradable polylactic acid, although it encounters constraints in biomedical applications as a result of inadequate mechanical characteristics. This study investigates the effects of atmospheric pressure plasma generated by a dielectric barrier discharge system using helium and/or argon on the modification of polylactic acid surfaces, changes in their wettability properties, and alterations in their chemical composition. The plasma source was ignited in either He or Ar and was tailored to fit the best operational conditions for polymer exposure. The results demonstrated the enhanced wettability of the polymer surface following plasma treatment (up to 40% in He and 20% in Ar), with a marginal variation observed among treatments utilizing different gases. The plasma treatments also caused changes in the surface topography, morphology, roughness, and hydrophilicity. Plasma exposure also resulted in observable modifications in the dielectric characteristics, phase transition, and structure. The experimental findings endorse the utilization of plasma technologies at normal air pressure for environmentally friendly processing of polymer materials, specifically for applications that necessitate enhanced adhesion and have carefully selected prerequisites.
The paper presents the synthesis and characterization of new cobalt ferrite-lignin hybrids. The hybrids were obtained through the combustion of cobalt nitrate and ferric nitrate, two kinds of lignin ...being used as combustion agents. The temperatures of calcination were 500 °C and 900 °C, respectively. The hybrids were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The magnetic properties were also assessed by vibrating sample magnetometer system (VSM). This facile synthesis method made it possible to obtain cobalt ferrite-lignin hybrids with a spinel structure. Their particle sizes and crystallite sizes have increased with an increment in the calcination temperature. A different occupancy of cations at octahedral and tetrahedral sites also occurred upon the increase in temperature. The hybrids comprising organic lignin presented the best magnetic properties.
Recent research has focused on molecules with different aromatic nitrogen-containing moieties coupled to a biphenyl core, as an effective approach for the assembly of coordination polymers. This ...study presents the synthesis and characterization of new ligands based on 1,1′-(3,3′-dimethoxy-1,1′-biphenyl-4,4′-diyl)bis(4-butyl-1H-1,2,3-triazole) (L1) and 1,1′-(3,3′-dimethoxy-1,1′-biphenyl-4,4′-diyl)bis(4-phenyl-1H-1,2,3-triazole) (L2) and their coordination polymers with Cu(II) and Zn(II). An unexpected coordination polymer with Cu(I) starting from Cu(II) was obtained in the case of the L2 ligand. The ligands and metal complexes underwent thorough characterization, including X-ray diffraction, NMR-, FTIR-, MS-spectrometry, and EPR, XPS, and TG-DTG analyses. While the ligand L2 generated a linear Cu(I) polymer, the ligand L1 formed a zigzag polymer with both copper and zinc.
Coordination polymers of 2′,3′,5′,6′-tetramethyl-1,1′:4′,1′′-terphenyl-4,4′′-dicarboxylic acid with Cu(II), Co(II) and Cd(II) have been synthesized and characterized by IR spectroscopy, single ...crystal X-ray diffraction, thermogravimetric analysis and nitrogen sorption studies.
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Three new 3D-metal–organic frameworks based on 2′,3′,5′,6′-tetramethyl-1,1′:4′,1′′-terphenyl-4,4′′-dicarboxylic acid (H2L) and Co, Cu, and Cd nodes have been synthesized. The complexes were characterized by elemental, thermogravimetric analysis, IR spectroscopy, single crystal, powder X-ray diffraction and gas sorption experiments. The crystal structure of Cu2L2(H2O)2n (1) corresponds to a two-dimensional coordination polymer, in which the metal nodes are two crystallographically equivalent Cu(II) atoms linked by four μ2-O,O′ carboxylate ligands in a centrosymmetric {Cu2O10} paddle-wheel building block. The structure of compound CoL(dmso)n (2) has a 3D metal–organic coordination lattice, in which the metal centers are connected by the linear organic ligand to generate a dense three-dimensional coordination polymer. Also, a three-dimensional coordination network was identified in the case of compound Cd2L2(dmf)n (3), whose structure is very similar to that of compound 2. In compound 3, the carboxylate groups of the linear L2− spacers behave as μ2-κ3O, O′:O tridentate bridging ligands. The compounds have a high thermal stability. Polymers 3 and 1 have moderate porosity (specific surface areas of approximately 900 m2/g and 600 m2/g, respectively), while polymer 2 has a dense structure.
Microbial infections represent a significant health risk, often leading to severe complications and, in some cases, even fatalities. As a result, there is an urgent need to explore innovative drug ...delivery systems and alternative therapeutic techniques. The photothermal therapy has emerged as a promising antibacterial approach and is the focus of this study. Herein, we report the successful synthesis of two distinct supramolecular composite hydrogels by incorporating graphene oxide (GO) and single-walled carbon nanotubes (SWNTs) into guanosine quadruplex (G4) based hydrogels containing covalently bound β-cyclodextrin (β-CD). The G4 matrix was synthesized through a two-step process, establishing a robust network between G4 and β-CDs, followed by the encapsulation of either GO or SWNTs. Comprehensive characterization of these composite hydrogels were conducted using analytical techniques, including circular dichroism, Raman spectroscopy, rheological investigations, X-ray diffraction, and scanning electron microscopy. A notable discovery from the conducted research is the differential photothermal responses exhibited by the hydrogels when exposed to near-infrared laser irradiation. Specifically, SWNT-based hydrogels demonstrated superior photothermal performance, achieving a remarkable temperature increase of up to 52 °C, in contrast to GO-based hydrogels, which reached a maximum of 34 °C. These composite hydrogels showed good cytotoxicity evaluation results and displayed synergistic antibacterial activity against Staphylococcus aureus, positioning them as promising candidates for antibacterial photothermic platforms, particularly in the context of wound treatment. This study offers a valuable contribution to the development of advanced and combined therapeutic strategies for combating microbial infections and highlights the potential of carbon nanomaterial-enhanced supramolecular hydrogels in photothermal therapy applications.
Three new Metal-Organic Frameworks, containing mesitylene tribenzoic acid as a linker and zinc (1) or cadmium as metals (2,3), were synthesized through solvothermal reactions, using DMF/ethanol/water ...as solvents, at temperatures of 80 °C (structures 1 and 3) and 120 °C (structure 2). Following single-crystal X-ray diffraction, it was found that 1 and 3 crystallize in the P21/c and C2/c space groups and form 2D networks, while 2 crystallizes in the Fdd2 space group, forming a 3D network. All three frameworks, upon heating, were found to be stable up to 350 °C. N2 sorption isotherms revealed that 1 displays a BET area of 906 m2/g. Moreover, the porosity of this framework is still present after five cycles of sorption/desorption, with a reduction of 14% of the BET area, down to 784 m2/g, after the fifth cycle. The CO2 loading capacity of 1 was found to be 2.9 mmol/g at 0 °C.
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