Dicyanamide-intertwined assembly of two new Zn complexes based on N2O4-type pro-ligand: Synthesis, crystal networks, spectroscopic insights, and selective nitroaromatic turn-off fluorescence sensing

Two new dicyanamide bridged multinuclear Zn complexes, [Zn₂(L¹)(µ_1,5-dca)₂(µ₁-dca)]_n (1) and [Zn₂(L²)(µ_1,5-dca)₂(µ₁-dca)]_n (2) have been synthesized using N₂O₄-based pro-ligands (H₂L¹ = N,N'-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane, H₂L² = N,N'-bis(3-ethoxysalicylidene)-2,2-dimethyl-1,3-propanediamine) and characterized by microanalytical and spectroscopic techniques. Both complexes are stable in solution and solid-state. Thermogravimetric analysis (TGA) findings showed that complexes are stable at room temperature. Single-crystal X-ray diffraction (SCXRD) has proven that complexes are identical structures where two zinc metal ions are crystallographically independent. The directional properties of dicyanamide co-ligands via µ_1,5 bridging have resulted in different connectivity of zinc metal ions leading to 1D templates. SCXRD revealed some notable non-covalent interactions (π⋯π, C-H····π, and H-bonding) in their solid-state crystal structures. 1-2 have strong fluorescence behaviour over pro-ligands, which may be quenched in the presence of various electron-deficient explosive nitroaromatic compounds (epNACs). Complex 2 fluorescence intensity is sharper than 1; hence the former retained high sensitivity and selectivity for trinitrophenol (TNP). The enhancement of fluorescence mechanism, detection limit (LOD), and the quenching constant (K_SV) have been calculated using the Stern-Volmer equation (SV), where the K_SV value for TNP is found to be 1.542 × 10⁴ M^-1. The solution phase quenching mechanism has been rationalized by (a) electrostatic interactions through charge-transfer complex, (b) photo-induced electron transfer (PET) by the HOMO-LUMO energy gap via DFT, and (c) fluorescence resonance energy transfer (FRET). Finally, complex 2 is applied as a sensor by turn-off fluorescence response to detecting TNP nitroaromatics in the DMF medium.

Ligands modulated the variable binuclear Cd2-SBUs and structures of four layered coordination frameworks

An intriguing modulation of Cd₂(RCOO)₄ SBUs and the structural variation in their layered CPs have been observed, which were tuned by di-carboxylate/co-ligand.

Studies on the influence of the nuclearity of zinc(ii) hemi-salen complexes on some pivotal biological applications

Experimental and theoretical corroboration of the various biological applications of two nuclearity-dependent dimeric and trimeric Zn(ii) hemi-salen complexes.

A series of trinuclear zinc(ii) complexes with reduced Schiff base ligands: turn-off fluorescent chemosensors with high selectivity for nitroaromatics

A series of trinuclear zinc(ii) complexes have been synthesized and characterized by X-ray crystallography. The ability of the complexes to act as sensors for the detection of nitroaromatics in DMF has been assessed.

Structural Diversity of Three Pyrazoyl-Carboxyl Bifunctional Ligand-Based Metal-Organic Frameworks: Luminescence and Magnetic Properties

Three metal-organic frameworks (MOFs), [Cd(Hpzbpdc)(H₂ O)]⋅H₂ O (1), [Mn₂ (Hpzbpdc)₂ (dmf)₂ ] (2), and [H₂ N(CH₃ )₂ ]_0.5 [Eu(Hpzbpdc)_1.5 (HCOO)_0.5 (dmf)_0.5 ]⋅DMF⋅0.5 H₂ O (3) (H₃ pzbpdc=4'-(2 H-pyrazol-3-yl)biphenyl-3,5-dicarboxylic acid), have been solvothermally synthesized from one pyrazoyl-carboxyl bifunctional ligand and characterized by single-crystal structures. The H₃ pzbpdc ligand in 1-3 displays various coordination modes through the pyrazoyl and carboxyl groups. Both 1 and 3 contain dinuclear cluster building units and reveal a four-connected gismondine (gis) zeolite 3D framework and a 2D grid layer structure, respectively. Compound 1 shows blue luminescence, compound 3 reveals red luminescence that arises from efficient energy transfer from the organic ligand to the europium(III) ion, and compound 2 reveals an uncommon (3,8)-connected tfz-d; UO₃ net with a rare Mn₄ (COO)₆ cluster and shows antiferromagnetic interactions between the manganese(II) ions.

A unique 3D metal-organic framework based on a 12-connected pentanuclear Cd(II) cluster exhibiting proton conduction

Solvothermal reaction of a TCA (TCA = 4,4',4''-tricarboxytriphenylamine) ligand with Cd(NO3)2 yielded a unique 3D 12-connected metal-organic framework of , which can be simplified as a (3,3,12)-connected 3-nodal net with a Schläfli symbol of {4(16)·6(36)·8(14)}{4(2)·6}2{4(3)}2 based on a 12-connected node of a pentanuclear Cd(ii) cluster and a three-connected organic linker of TCA. Compound exhibits both photoluminescence and proton conductivity. The luminescence properties of originate from the triphenylamine chromophore of the TCA ligand. The proton conductivity of is supposed to be relevant to the structure attributes of . On the one hand, the curved narrow channels lined with a hydrophilic pentanuclear Cd(ii) cluster in can improve the water affinity of framework and facilitate the water absorption under humid conditions. On the other hand, the coordinated water molecules within the pentanuclear Cd(ii) cluster can produce a mobile H(+) proton due to coordination activation. At 80 °C and 85% RH (relative humidity), compound shows the proton conductivity of 1.45 × 10(-6) S cm(-1).

Metal(ii)–organic frameworks with 3,3′-diphenyldicarboxylate and 1,3-bis(4-pyridyl)propane: preparation, crystal structures and luminescence

3D frameworks were constructed from Zn(ii)/Cd(ii)/Cu(ii), 3,3′-diphenyldicarboxylate, and 1,3-bis(4-pyridyl)propane. The Zn-framework was used as a fluorescent probe to sense benzaldehyde.

Synthesis, Crystal Structures and Properties of Two-dimensional Complexes Constructed by Dicarboxylate and Bis(Imidazole) Co-ligands

The complexes {[Zn(1,3-bip)(3,5-pdc)]·2H2O}n and {[Cu(1,3-bip)(1,3-bdc)]·H2O}n, [1,3-bip=1,3-bis(imidazole)propane, 3,5-pdc=pyridine-3,5-dicarboxylic acid, 1,3-bdc=isophthalic acid], have been synthesised under hydrothermal conditions and structurally characterised. Their thermogravimetric and photoluminescence properties were also investigated.

Poly[(μ(2)-1,3-di-4-pyridyl-propane)(μ(3)-1,3-phenyl-enediacetato)-cadmium]

In the title compound, [Cd(C₁₀H₈O₄)(C₁₃H₁₄N₂)]_n, two symmetry-related Cd atoms are bridged by two carboxyl­ate O atoms into a binuclear Cd₂ subunit around an inversion center. The Cd atom has a distorted penta­gonal–bipyramidal environment, defined by five O atoms from three different 1,3-phenylendiacetate (1,3-pda) ligands and two N atoms from two 1,3-di-4-pyridyl­propane (bpp) ligands. Each Cd₂ subunit is linked to four different Cd₂ subunits by four 1,3-pda ligands and four bpp ligands, forming a two-dimensional network with rhombic grids (12.50 × 12.50 Ų) extending along the ab plane.