Ni^II₂₀ “Bowls” from the Use of Tridentate Schiff Bases

The reactions of <i>N</i>-salicylidene-<i>o</i>-aminophenol or its derivatives and excess of nickel­(II) acetate in alcohols have led to Ni^II₂₀ clusters with an unprecedented “bowl” metal topology

Ni^II₂₀ “Bowls” from the Use of Tridentate Schiff Bases

The reactions of <i>N</i>-salicylidene-<i>o</i>-aminophenol or its derivatives and excess of nickel­(II) acetate in alcohols have led to Ni^II₂₀ clusters with an unprecedented “bowl” metal topology

Structural–Spectrochemical Correlations of Variable Dimensionality Crystalline Metal–Organic Framework Materials in Hydrothermal Reactivity Patterns of Binary–Ternary Systems of Pb(II) with (a)Cyclic (Poly)carboxylate and Aromatic Chelator Ligands

Efforts to comprehend the structural–spectrochemical correlations of crystalline metal–organic framework materials of Pb­(II) with (a)­cyclic and aromatic chelators linked to photoluminescent applications led to the hydrothermal pH-specific synthesis of crystalline materials [Pb­{H₂BTC}­(phen)­(H₂O)]_<i>n</i>·2<i>n</i>H₂O­(<b>1</b>), [Pb₂{CBTC}]_<i>n</i>(<b>2</b>), [Pb₄(phen)₈{CBTC}₂(H₂O)₄]₃·70.3H₂O­(<b>3</b>), and [Pb­{HCTA}­(H₂O)₂]_<i>n</i>·<i>n</i>H₂O­(<b>4</b>). X-ray studies showed that <b>1</b>–<b>4</b> exhibit unique architectures linked to 2D–3D coordination polymers formulated by Z-type units composed of Pb₂O₂ cores, unusually high number of lattice–water molecules, and π–π and H-bond interactions. The contribution of the nature–structure properties of the aliphatic-(a)­cyclic organic (poly)­carboxylic/aromatic chelators-ligands to binary-ternary Pb­(II) reactivity weaves into the assembly of supramolecular networks, thereby providing clear structural–spectroscopic inter-relationships exemplifying the observed photoluminescent activity in a distinct MOF-linked fashion

Structural–Spectrochemical Correlations of Variable Dimensionality Crystalline Metal–Organic Framework Materials in Hydrothermal Reactivity Patterns of Binary–Ternary Systems of Pb(II) with (a)Cyclic (Poly)carboxylate and Aromatic Chelator Ligands

Efforts to comprehend the structural–spectrochemical correlations of crystalline metal–organic framework materials of Pb­(II) with (a)­cyclic and aromatic chelators linked to photoluminescent applications led to the hydrothermal pH-specific synthesis of crystalline materials [Pb­{H₂BTC}­(phen)­(H₂O)]_<i>n</i>·2<i>n</i>H₂O­(<b>1</b>), [Pb₂{CBTC}]_<i>n</i>(<b>2</b>), [Pb₄(phen)₈{CBTC}₂(H₂O)₄]₃·70.3H₂O­(<b>3</b>), and [Pb­{HCTA}­(H₂O)₂]_<i>n</i>·<i>n</i>H₂O­(<b>4</b>). X-ray studies showed that <b>1</b>–<b>4</b> exhibit unique architectures linked to 2D–3D coordination polymers formulated by Z-type units composed of Pb₂O₂ cores, unusually high number of lattice–water molecules, and π–π and H-bond interactions. The contribution of the nature–structure properties of the aliphatic-(a)­cyclic organic (poly)­carboxylic/aromatic chelators-ligands to binary-ternary Pb­(II) reactivity weaves into the assembly of supramolecular networks, thereby providing clear structural–spectroscopic inter-relationships exemplifying the observed photoluminescent activity in a distinct MOF-linked fashion

Investigating Magnetostructural Correlations in the Pseudooctahedral <i>trans</i>-[Ni^II{(OPPh₂)(EPPh₂)N}₂(sol)₂] Complexes (E = S, Se; sol = DMF, THF) by Magnetometry, HFEPR, and ab Initio Quantum Chemistry

In this work, magnetometry and high-frequency and -field electron paramagnetic resonance spectroscopy (HFEPR) have been employed in order to determine the spin Hamiltonian (SH) parameters of the non-Kramers, <i>S</i> = 1, pseudooctahedral <i>trans</i>-[Ni^II{(OPPh₂)­(EPPh₂)­N}₂(sol)₂] (E = S, Se; sol = DMF, THF) complexes. X-ray crystallographic studies on these compounds revealed a highly anisotropic NiO₄E₂ coordination environment, as well as subtle structural differences, owing to the nature of the Ni^II-coordinated solvent molecule or ligand E atoms. The effects of these structural characteristics on the magnetic properties of the complexes were investigated. The accurately HFEPR-determined SH zero-field-splitting (zfs) <i>D</i> and <i>E</i> parameters, along with the structural data, provided the basis for a systematic density functional theory (DFT) and multiconfigurational ab initio computational analysis, aimed at further elucidating the electronic structure of the complexes. DFT methods yielded only qualitatively useful data. However, already entry level ab initio methods yielded good results for the investigated magnetic properties, provided that the property calculations are taken beyond a second-order treatment of the spin–orbit coupling (SOC) interaction. This was achieved by quasi-degenerate perturbation theory, in conjunction with state-averaged complete active space self-consistent-field calculations. The accuracy in the calculated <i>D</i> parameters improves upon recovering dynamic correlation with multiconfigurational ab initio methods, such as the second-order N-electron valence perturbation theory NEVPT2, the difference dedicated configuration interaction, and the spectroscopy-oriented configuration interaction. The calculations showed that the magnitude of <i>D</i> (∼3–7 cm^–1) in these complexes is mainly dominated by multiple SOC contributions, the origin of which was analyzed in detail. In addition, the observed largely rhombic regime (<i>E</i>/<i>D</i> = 0.16–0.33) is attributed to the highly distorted metal coordination sphere. Of special importance is the insight by this work on the zfs effects of Se coordination to Ni^II. Overall, a combined experimental and theoretical methodology is provided, as a means to probe the electronic structure of octahedral Ni^II complexes

Synthesis and Characterization of <i>fac</i>-[M(CO)₃(P)(OO)] and <i>cis-trans</i>-[M(CO)₂(P)₂(OO)] Complexes (M = Re, ^99mTc) with Acetylacetone and Curcumin as OO Donor Bidentate Ligands

The synthesis and characterization of neutral mixed ligand complexes <i>fac-</i>[M­(CO)₃(P)­(OO)] and <i>cis-trans</i>-[M­(CO)₂(P)₂(OO)] (M = Re, ^99mTc), with deprotonated acetylacetone or curcumin as the OO donor bidentate ligands and a phosphine (triphenylphosphine or methyldiphenylphosphine) as the monodentate P ligand, is described. The complexes were synthesized through the corresponding <i>fac-</i>[M­(CO)₃(H₂O)­(OO)] (M = Re, ^99mTc) intermediate aqua complex. In the presence of phosphine, replacement of the H₂O molecule of the intermediate complex at room temperature generates the neutral tricarbonyl monophosphine <i>fac</i>-[Re­(CO)₃(P)­(OO)] complex, while under reflux conditions further replacement of the trans to the phosphine carbonyl generates the new stable dicarbonyl bisphosphine complex <i>cis-trans</i>-[Re­(CO)₂(P)₂(OO)]. The Re complexes were fully characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral geometry around Re. Both the monophosphine and the bisphosphine complexes of curcumin show selective binding to β-amyloid plaques of Alzheimer’s disease. At the ^99mTc tracer level, the same type of complexes, <i>fac</i>-[^99mTc­(CO)₃(P)­(OO)] and <i>cis-trans</i>-[^99mTc­(CO)₂(P)₂(OO)], are formed introducing new donor combinations for ^99mTc­(I). Overall, β-diketonate and phosphine constitute a versatile ligand combination for Re­(I) and ^99mTc­(I), and the successful employment of the multipotent curcumin as β-diketone provides a solid example of the pharmacological potential of this system

pH-Specific Crystalline Binary and Ternary Metal–Organic Framework Materials of Pb(II) with (Di)Tricarboxylate Ligands and <i>N</i>,<i>N</i>′‑Aromatic Chelators. Structure, Architecture-Lattice Dimensionality, and Electronic Spectroscopic Property Correlations

Efforts to probe and delineate intricate structure–property relationships key to the development of crystalline Pb­(II)-containing metal–organic framework materials led to the design and pH-specific hydrothermal synthetic investigation of binary/ternary Pb­(II)-(di)­tricarboxylate ligand (succinic, glutaric, tricarballylic acids) systems in the presence of variable-nature aromatic N,N′-chelators bipyridine (bpy)/phenanthroline (phen). The arisen crystalline materials [Pb­(phen)­(suc)]_<i>n</i> (<b>1</b>), [Pb₃(phen)₃­(glu)₃]_<i>n</i>­·7<i>n</i>H₂O (<b>2</b>), [Pb₃(tca)₂]<i>_n</i> (<b>3</b>), and [Pb₂(phen)₂­(tcaH)₂]_<i>n</i>­·<i>n</i>H₂O (<b>4</b>) provide evidence for structural correlations linking the nature of ligands with Pb­(II) chemistry and the emerging crystalline-polymeric assemblies. Detailed physicochemical characterization (Fourier transform infrared spectroscopy, ¹³C-,²⁰⁷Pb-cross polarization magic angle spinning NMR, thermogravimetric analysis, luminescence) reveals distinct architecture, lattice dimensionality (2D-3D), and luminescence property correlations and identifies structural and electronic factors interweaving into the design of functional materials

Synthesis and Characterization of <i>fac</i>-[M(CO)₃(P)(OO)] and <i>cis-trans</i>-[M(CO)₂(P)₂(OO)] Complexes (M = Re, ^99mTc) with Acetylacetone and Curcumin as OO Donor Bidentate Ligands

The synthesis and characterization of neutral mixed ligand complexes <i>fac-</i>[M­(CO)₃(P)­(OO)] and <i>cis-trans</i>-[M­(CO)₂(P)₂(OO)] (M = Re, ^99mTc), with deprotonated acetylacetone or curcumin as the OO donor bidentate ligands and a phosphine (triphenylphosphine or methyldiphenylphosphine) as the monodentate P ligand, is described. The complexes were synthesized through the corresponding <i>fac-</i>[M­(CO)₃(H₂O)­(OO)] (M = Re, ^99mTc) intermediate aqua complex. In the presence of phosphine, replacement of the H₂O molecule of the intermediate complex at room temperature generates the neutral tricarbonyl monophosphine <i>fac</i>-[Re­(CO)₃(P)­(OO)] complex, while under reflux conditions further replacement of the trans to the phosphine carbonyl generates the new stable dicarbonyl bisphosphine complex <i>cis-trans</i>-[Re­(CO)₂(P)₂(OO)]. The Re complexes were fully characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral geometry around Re. Both the monophosphine and the bisphosphine complexes of curcumin show selective binding to β-amyloid plaques of Alzheimer’s disease. At the ^99mTc tracer level, the same type of complexes, <i>fac</i>-[^99mTc­(CO)₃(P)­(OO)] and <i>cis-trans</i>-[^99mTc­(CO)₂(P)₂(OO)], are formed introducing new donor combinations for ^99mTc­(I). Overall, β-diketonate and phosphine constitute a versatile ligand combination for Re­(I) and ^99mTc­(I), and the successful employment of the multipotent curcumin as β-diketone provides a solid example of the pharmacological potential of this system