Tuning the Functional Properties of Metal Complexes Containing Polytopic Heteroaromatic Nitrogen Ligands

4,7-Substituted 1,10-phenanthroline-2,9-dicarboxamides: photophysics of ligands and their complexes with the Eu-Gd-Tb triad

The impact of substituents at the 4- and 7-positions of 1,10-phenanthroline-2,9-dicarboxamides on the photophysical properties of the ligands and their coordination compounds with the lanthanide triad-europium, gadolinium, and terbium-was analyzed. This study demonstrates how modification of the electronic nature of ligands through the incorporation of diverse functional groups affects the luminescence properties of their complexes. The introduction of various substituents leads to the appearance of intra-ligand or ligand-to-ligand charge transfer (CT) states. The highest luminescence efficiency was observed for LH·Eu(NO3)3 (Qin = 54.1% and QL = 9.6%), suggesting strong luminescence quenching of the CT state. It was found that a relatively low ΔE (∼3000 cm-1) supports direct energy transfer from S1 to T1 bypassing the CT state, even though it is outside Reinhoudt's optimal range. The introduction of fluorines leads to the strongest luminescence quenching among all the substituents.

Heteroleptic cobalt complex augments antifungal activity with fluconazole and causes membrane disruption in Candida albicans

Heteroleptic metal complexes containing CuII, CoII, and ZnII, incorporating curcumin and a Schiff base ligand (L), were synthesized and characterized, and their antifungal activity was evaluated. Their antifungal activities were investigated individually and in combination with fluconazole. Utilizing various analytical techniques such as UV-Vis, FT-IR, NMR, ESI-MS, TGA-DTG, elemental analyses, conductance, and magnetic susceptibility measurements, complex C1 ([Cu(Cur)LCl(H2O)]) was assigned a distorted octahedral geometry, while complexes C2 ([Co(Cur)LCl(H2O)]) and C3 ([Zn(Cur)LCl(H2O)]) were assigned octahedral geometries. Among these complexes, C2 exhibited the highest inhibitory activity against both FLC-susceptible and resistant strains of Candida albicans. Furthermore, C2 demonstrated candidicidal activity and synergistic interactions with fluconazole, effectively inhibiting the growth and survival of both FLC-resistant and FLC-sensitive C. albicans strains. The complex displayed a dose-dependent inhibition of drug efflux pumps in FLC-resistant C. albicans strains, indicating its potential to disrupt the cell membrane of these strains. The significant role of membrane efflux transporters in the development of antifungal drug resistance within Candida species has been extensively documented and our findings indicate that complex C2 specifically targets this crucial factor, thereby playing a pivotal role in mitigating drug resistance in C. albicans.

Integration of Trinuclear Triangle Copper(II) Secondary Building Units in Octacyanidometallates(IV)-Based Frameworks

The design and synthesis of high-dimensional materials based on secondary building blocks (SBUs) play a pivotal role in the further development of functional molecular materials. Herein, the self-assembly of Cu(II) ions, pyrazole (Hpz), and octacyanidometallate(IV) anions in the presence of water produced two new isostructural three-dimensional systems {[Cu₃(μ₃-OH)(μ-pz)₃(H₂O)₃]₂[M(CN)₈]}·nH₂O (M = W, 1, and Mo, 2). 1 and 2 consist of trinuclear triangle copper(II) (TTC) SBUs and octacyanidometallates(IV). At room temperature, both assemblies display strong antiferromagnetic interactions within the TTC entities with an average Cu^II···Cu^II isotropic magnetic coupling constant of about -145 cm^-1. Moreover, a detailed analysis of magnetic data revealed the presence of spin frustration with antisymmetric magnetic exchange-coupling constants of around +32 and +46 cm^-1 for 1 and 2, respectively. Finally, quantum chemical calculations explained their magnetic and optical properties.

Low-temperature crystal structure of 4-chloro-1H-pyrazole

The structure of 4-chloro-1H-pyrazole, C3H3ClN2, at 170 K has ortho-rhom-bic (Pnma) symmetry and is isostructural to its bromo analogue. Data were collected at low temperature since 4-chloro-1H-pyrazole sublimes when subjected to the localized heat produced by X-rays. The structure displays inter-molecular N-H⋯N hydrogen bonding and the packing features a trimeric mol-ecular assembly bis-ected by a mirror plane (m normal to b) running through one chlorine atom, one carbon atom and one N-N bond. The asymmetric unit therefore consists of one and one-half 4-chloro-1H-pyrazole mol-ecules. Thus, the N-H proton is crystallographically disordered over two positions of 50% occupancy each.

Advanced Functional Luminescent Metallomesogens: The Key Role of the Metal Center

The use of liquid crystals for the fabrication of displays incorporated in technological devices (TVs, calculators, screens of eBook's, tablets, watches) demonstrates the relevance that these materials have had in our way of living. However, society evolves, and improved devices are looked for as we create a more efficient and safe technology. In this context, metallomesogens can behave as multifunctional materials because they can combine the fluidic state of the mesophases with properties such as photo and electroluminescence, which offers new exciting possibilities in the field of optoelectronics, energy, environment, and even biomedicine. Herein, it has been established the role of the molecular geometry induced by the metal center in metallomesogens to achieve the self-assembly required in the liquid-crystalline mesophase. Likewise, the effect of the coordination environment in metallomesogens has been further analyzed because of its importance to induce mesomorphism. The structural analysis has been combined with an in-depth discussion of the properties of these materials, including their current and potential future applications. This review will provide a solid background to stimulate the development of novel and attractive metallomesogens that allow designing improved optoelectronic and microelectronic components. Additionally, nanoscience and nanotechnology could be used as a tool to approach the design of nanosystems based on luminescent metallomesogens for use in bioimaging or drug delivery.

Three Mn(ii) metal–organic frameworks with the same chemical composition, but different topological structures and properties

Solvothermal reactions of a novel multidentate ligand, 2,5-bis-(1,2,4-triazol-1-yl)-terephthalic acid (H₂TTPA), with MnCl₂ afforded three structurally distinct coordination polymers with the same formula, [Mn(TTPA)·H₂O]_n (Mn-(1–3)).

Solvent-controlled metal coordination polymers of Co(ii) with different topological structures and properties

Three multidimensional Co-polymers were obtained. Co-1 exhibits as a 2D layer. Co-2 displays as a tetranodal (4,4,5,6)-connected 3D MOFs. Co-3 is a binodal (4,6)-connected 3D framework.

Synthesis, crystal structure, and optical properties of fluorinated poly(pyrazole) ligands and in silico assessment of their affinity for volatile organic compounds

Increasing fluorination of an organic ligand forming porous coordination polymers results in enhanced affinity for volatile organic compounds (VOCs) without affecting the fluorescence properties, thus opening new perspectives for VOC sensing.

Structural diversity of ethylzinc derivatives of 3,5-substituted pyrazoles

Equimolar reactions of Et2Zn with 3,5-dimethylpyrazole (H-pzMe2), 3,5-di-iso-propylpyrazole (H-pziPr2), 3,5-di-tert-butylpyrazole (H-pztBu2) and indazole (H-ind) were investigated in toluene or tetrahydrofuran (as a coordinating solvent). A series of diverse ethylzinc pyrazolates and indazolates were identified using advanced NMR spectroscopy and the single crystal X-ray diffraction techniques. The NMR experiments indicate that dimeric moieties of the general formula [EtZn(pz)]2 or [Et2Zn2(pz)2(THF)] are favoured in solution. Nevertheless, these types of complexes are kinetically labile and tend to undergo ligand scrambling reactions according to the Schlenk equilibrium. For example, the alkyl substituents in the pzMe2 and pziPr2 ligands do not appear to be a strong determinant of the dimeric moieties and the composition of the isolated complexes by crystallisation from the parent reaction mixture varies between spiro-type tri- and tetranuclear aggregates, [Et2Zn3(pz)4(THF)x] (x = 0 or 2) and [Et2Zn4(pz)6(THF)2], respectively. The nonstoichiometric formula of these organozinc derivatives is likely related to both the Schlenk-type equilibria and solubility of the respective moieties. In turn, the high steric demands of the 3,5-di-tert-butylpyrazolate ligand promote the dimeric form in solution and the solid state. Interestingly, the ethylzinc indazolate complex also does not undergo a redistribution reaction and yields a dimer.

Coordination polymers based on pyrazole-4-carboxaldehyde-containing Cu3N6 metallacycles as building units

Two novel topologies were obtained by self-assembly of 4-formylpyrazolate-Cu₃ SBUs in the absence of competing terminal ligands.

Interactions between H-bonded [CuII3(μ3-OH)] triangles; a combined magnetic susceptibility and EPR study

X-band EPR spectroscopy and magnetic susceptibility studies elucidate the magnetic exchange scheme within a triangular CuII3(μ₃-OH) complex and the intermolecular dipolar interactions between two H-bonded CuII3(μ₃-OH) units.

Two isostructural fluorinated metal-organic frameworks with rare rod-packing architecture: syntheses, structures and luminescent properties

Two isostructural fluorinated metal-organic frameworks, formulated as [M 2(Fbix)(1,4-NDC)2] n (M=Cd for 1 and Mn for 2), were synthesized by employing 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) and the flexible fluorinated ligand 2,3,5,6-tetrafluoro-1,4-bis(imidazole-1-yl-methyl)benzene (Fbix) under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction and further characterized by infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analyses. Structure analyses have revealed that compounds 1 and 2 show an unusual hex net based on infinite rod-shaped secondary building units. The solid-state fluorescence spectra of 1 and 2 were measured and indicate a ligand-based emission for both complexes.

A series of coordination polymers based on terphenyl tetracarboxylates and bis-pyridyl ligands with water vapor sorption properties

Six new coordination polymers have been synthesized based on terphenyl tetracarboxylates (H₄L1, H₄L2) and bis-pyridyl ligands (bpfp, bpe and bpmp).

Functional group effects on structure and topology of cadmium(ii) frameworks with mixed organic ligands

Cadmium(ii) complexes were obtained by tuning functional groups of benzenedicarboxylate and reaction conditions, their ferroelectric and photoluminescence properties were studied.

Vapochromic properties versus metal ion coordination of β-bispyrazolato–copper(ii) coordination polymers: a first-principles investigation

Vapochromic properties of Cu(ii) coordination polymers are explained on the basis of first principles calculations.

Functionalities and architectures of coordination polymers with multi-dimensionalities via transition metal–dicarboxylate ligands

Five coordination polymers based on the flexible H₂dpd ligand and different metal salts have been synthesised. The configuration of the ligand and the reaction temperature have important effects on the final structures.

Nickel(ii) and copper(i,ii)-based metal-organic frameworks incorporating an extended tris-pyrazolate linker

The synthesis, thermal behavior, crystal structure and adsorption properties of two novel MOFs isolated by coupling Ni(ii) and Cu(ii) to the extended tris(pyrazolate) strut 1,3,5-tris((1H-pyrazol-4-yl)phenyl)benzene are reported.

Solvent-free heterogeneous catalysis for cyanosilylation in a modified sodalite-type Cu(ii)-MOF

Modified sodalite-type Cu–BTT MOF is an active solvent-free heterogeneous catalyst for cyanosilylation. The catalyst loading is only one eleventh of that for related Mn–BTT but conversion of benzaldehyde is 96%. These properties make the modified MOF an ideal green catalyst.

Synthesis of a series of coordination polymers based on mixed ligands to tune the structural dimension

Schematic illustrating the 2D network of complex 1. Color code: yellow, Mn; cob²⁻ ligand, red.

Antibacterial action of 4,4'-bipyrazolyl-based silver(I) coordination polymers embedded in PE disks

Coupling the rigid spacer 4,4'-bipyrazole (H(2)BPZ), in its anionic or neutral form, to different silver(I) salts allowed isolation of the novel coordination polymers [Ag(2)(BPZ)] (1) and [Ag(H(2)BPZ)(X)] (X = NO(3), 2; ClO(4), 3; BF(4), 4; PF(6), 5; CH(3)SO(3), 6; CF(3)SO(3), 7), which were fully characterized by infrared and emission spectroscopies, thermal analysis, and X-ray powder diffraction. The crystal structure of 1 consists of 2-D layers containing 1-D chains of Ag(I) ions bridged by exo-tetradentate bipyrazolato moieties. The crystal structures of the [Ag(H(2)BPZ)(X)] species 2-7 feature 1-D chains of [Ag(H(2)BPZ)] stoichiometry, along which the metal centers are bridged by exo-bidentate bipyrazolyl spacers. Contacts among adjacent chains are mediated by the counterions through nonbonding interactions involving the Ag(I) ions and the pyrazolyl N-H groups. Thermogravimetric analyses disclosed the good thermal stability of these materials, decomposing in the range 200-300 °C. Under UV irradiation at room temperature, all the species showed a yellow-green emission centered in the range 520-522 nm. When embedded into polyethylene disks, 1, 2, and 4-7 demonstrated their activity as topical antibacterial agents against suspensions of E. coli, P. aeruginosa, and S. aureus: complete reduction of the three bacterial strains was achieved in 24 h, reduction of S. aureus reaching ca. 90% in only 2 h. Biocidal action was expressed also by contact susceptibility tests.