Cu^II-Azide Polynuclear Complexes of Three Different Building Clusters with the Same Schiff-Base Ligand: Synthesis, Structures, Magnetic Behavior, and Density Functional Theory Studies

Three copper-azido complexes [Cu₄(N₃)₈(L¹)₂­(MeOH)₂]_<i>n</i> (<b>1</b>), [Cu₄(N₃)₈(L¹)₂] (<b>2</b>), and [Cu₅(N₃)₁₀(L¹)₂]_<i>n</i> (<b>3</b>) [L¹ is the imine resulting from the condensation of pyridine-2-carboxaldehyde with 2-(2-pyridyl)­ethylamine] have been synthesized using lower molar equivalents of the Schiff base ligand with Cu­(NO₃)₂·3H₂O and an excess of NaN₃. Single crystal X-ray structures show that the basic unit of the complexes <b>1</b> and <b>2</b> contains Cu^II₄ building blocks; however, they have distinct basic and overall structures due to a small change in the bridging mode of the peripheral pair of copper atoms in the linear tetranuclear structures. Interestingly, these changes are the result of changing the solvent system (MeOH/H₂O to EtOH/H₂O) used for the synthesis, without changing the proportions of the components (metal to ligand ratio 2:1). Using even lower proportions of the ligand, another unique complex was isolated with Cu^II₅ building units, forming a two-dimensional complex (<b>3</b>). Magnetic susceptibility measurements over a wide range of temperature exhibit the presence of both antiferromagnetic (very weak) and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional, and two different basis sets) have been performed on the complexes <b>1</b> and <b>2</b> to provide a qualitative theoretical interpretation of their overall magnetic behavior

Cu^II-Azide Polynuclear Complexes of Three Different Building Clusters with the Same Schiff-Base Ligand: Synthesis, Structures, Magnetic Behavior, and Density Functional Theory Studies

Three copper-azido complexes [Cu₄(N₃)₈(L¹)₂­(MeOH)₂]_<i>n</i> (<b>1</b>), [Cu₄(N₃)₈(L¹)₂] (<b>2</b>), and [Cu₅(N₃)₁₀(L¹)₂]_<i>n</i> (<b>3</b>) [L¹ is the imine resulting from the condensation of pyridine-2-carboxaldehyde with 2-(2-pyridyl)­ethylamine] have been synthesized using lower molar equivalents of the Schiff base ligand with Cu­(NO₃)₂·3H₂O and an excess of NaN₃. Single crystal X-ray structures show that the basic unit of the complexes <b>1</b> and <b>2</b> contains Cu^II₄ building blocks; however, they have distinct basic and overall structures due to a small change in the bridging mode of the peripheral pair of copper atoms in the linear tetranuclear structures. Interestingly, these changes are the result of changing the solvent system (MeOH/H₂O to EtOH/H₂O) used for the synthesis, without changing the proportions of the components (metal to ligand ratio 2:1). Using even lower proportions of the ligand, another unique complex was isolated with Cu^II₅ building units, forming a two-dimensional complex (<b>3</b>). Magnetic susceptibility measurements over a wide range of temperature exhibit the presence of both antiferromagnetic (very weak) and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional, and two different basis sets) have been performed on the complexes <b>1</b> and <b>2</b> to provide a qualitative theoretical interpretation of their overall magnetic behavior

Molecular Marriage through Partner Preferences in Covalent Cage Formation and Cage-to-Cage Transformation

Unprecedented self-sorting of three-dimensional purely organic cages driven by dynamic covalent bonds is described. Four different cages were first synthesized by condensation of two triamines and two dialdehydes separately. When a mixture of all the components was allowed to react, only two cages were formed, which suggests a high-fidelity self-recognition. The issue of the preference of one triamine for a particular dialdehyde was further probed by transforming a non-preferred combination to either of the two preferred combinations by reacting it with the appropriate triamine or dialdehyde

New Structural Topologies in a Series of 3d Metal Complexes with Isomeric Phenylenediacetates and 1,3,5-Tris(1-imidazolyl)benzene Ligand: Syntheses, Structures, and Magnetic and Luminescence Properties

In this article we present the syntheses, characterizations, magnetic and luminescence properties of five 3d-metal complexes, [Co­(tib)­(1,2-phda)]_<i>n</i>­·(H₂O)_<i>n</i> (<b>1</b>), [Co₃(tib)₂­(1,3-phda)₃­(H₂O)]_<i>n</i>­·(H₂O)_2<i>n</i> (<b>2</b>), [Co₅(tib)₃­(1,4-phda)₅­(H₂O)₃]_<i>n</i>­·(H₂O)_7<i>n</i> (<b>3</b>), [Zn₃(tib)₂­(1,3-phda)₃]_<i>n</i>­·(H₂O)_4<i>n</i> (<b>4</b>), and [Mn­(tib)₂­(H₂O)₂]_<i>n</i>­·(1,4-phdaH)_2<i>n</i>­·(H₂O)_4<i>n</i> (<b>5</b>), obtained from the use of isomeric phenylenediacetates (phda) and the neutral 1,3,5-tris­(1-imidazolyl)­benzene (tib) ligand. Single crystal X-ray structures showed that <b>1</b> constitutes 3,5-connected 2-nodal nets with a double-layered two-dimensional (2D) structure, while <b>2</b> forms an interpenetrated 2D network (3,4-connected 3-nodal net). Complex <b>3</b> has a complicated three-dimensional structure with 10-nodal 3,4,5-connected nets. Complex <b>4</b>, although it resembles <b>2</b> in stoichiometry and basic building structures, forms a very different overall 2D assembly. In complex <b>5</b> the dicarboxylic acid, upon losing only one of the acidic protons, does not take part in coordination; instead it forms a complicated hydrogen bonding network with water molecules. Magnetic susceptibility measurements over a wide range of temperatures revealed that the metal ions exchange very poorly through the tib ligand, but for the Co­(II) complexes the effects of nonquenched orbital contributions are prominent. The 3d¹⁰ metal complex <b>4</b> showed strong luminescence with λ_max = 415 nm (for λ_ex = 360 nm)

Molecular Marriage through Partner Preferences in Covalent Cage Formation and Cage-to-Cage Transformation

Unprecedented self-sorting of three-dimensional purely organic cages driven by dynamic covalent bonds is described. Four different cages were first synthesized by condensation of two triamines and two dialdehydes separately. When a mixture of all the components was allowed to react, only two cages were formed, which suggests a high-fidelity self-recognition. The issue of the preference of one triamine for a particular dialdehyde was further probed by transforming a non-preferred combination to either of the two preferred combinations by reacting it with the appropriate triamine or dialdehyde

Two Novel Heterometallic Chains Featuring Mn^II and Na^I Ions in Trigonal-Prismatic Geometries Alternately Linked to Octahedral Mn^IV Ions: Synthesis, Structures, and Magnetic Behavior

Two new one-dimensional heterometallic complexes, [Mn₃Na­(L)₄(CH₃CO₂)­(MeOH)₂]­(ClO₄)₂·3H₂O (<b>1</b>), [Mn₃Na­(L)₄(CH₃CH₂CO₂)­(MeOH)₂]­(ClO₄)₂·2MeOH·H₂O (<b>2</b>) [LH₂ = 2-methyl-2-(2-pyridyl)­propane-1,3-diol], have been synthesized and characterized by X-ray crystallography. Both complexes feature Mn^II and Na^I ions in trigonal-prismatic geometries that are linked to octahedral Mn^IV ions by alkoxy bridges. Variable-temperature direct- and alternating-current magnetic susceptibility data indicated a spin ground state of <i>S</i> = ¹¹/₂ for both complexes. Density functional theory calculations performed on <b>1</b> supported this conclusion

Two Novel Heterometallic Chains Featuring Mn^II and Na^I Ions in Trigonal-Prismatic Geometries Alternately Linked to Octahedral Mn^IV Ions: Synthesis, Structures, and Magnetic Behavior

Two new one-dimensional heterometallic complexes, [Mn₃Na­(L)₄(CH₃CO₂)­(MeOH)₂]­(ClO₄)₂·3H₂O (<b>1</b>), [Mn₃Na­(L)₄(CH₃CH₂CO₂)­(MeOH)₂]­(ClO₄)₂·2MeOH·H₂O (<b>2</b>) [LH₂ = 2-methyl-2-(2-pyridyl)­propane-1,3-diol], have been synthesized and characterized by X-ray crystallography. Both complexes feature Mn^II and Na^I ions in trigonal-prismatic geometries that are linked to octahedral Mn^IV ions by alkoxy bridges. Variable-temperature direct- and alternating-current magnetic susceptibility data indicated a spin ground state of <i>S</i> = ¹¹/₂ for both complexes. Density functional theory calculations performed on <b>1</b> supported this conclusion

Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in Co^II Metal–Organic Frameworks

Single-crystal-to-single-crystal (SCSC) breathing and guest exchange properties of a series of Co^II metal–organic frameworks (MOFs) are reported. A new bis-pyridyl-bis-amide ligand, namely 4,4′-oxybis­(<i>N</i>-(pyridine-4-yl)­benzamide) (<b>LP1</b>), produced two MOFs, namely [{Co­(LP1)­(IPA)}­(DMF)₂(H₂O)]_∞ (<b>1</b>) and [{Co₂(LP1)₂(TPA)₂}­(DMF)₄]_∞ (<b>2</b>) under solvothermal conditions (IPA = isophthalate, TPA = terephthlate). While <b>1</b> showed excellent SCSC breathing responsive to both heat and guests (acetone, DMSO, MeOH, DEF), <b>2</b> displayed no breathing under similar conditions. However, it showed excellent SCSC guest (acetone, DMSO) exchange properties. Single-crystal structural analyses revealed that the conformational flexibility of the ligand <b>LP1</b> played a crucial role both in breathing in <b>1</b> and in guest exchange in <b>2</b>. Compound <b>1</b> also displayed heat responsive magnetic changes

Mechanistic Aspects for the Formation of Copper Dimer Bridged by Phosphonic Acid and Extending Its Dimensionality by Organic and Inorganic Linkers: Synthesis, Structural Characterization, Magnetic Properties, and Theoretical Studies

Six new copper metal complexes with formulas [Cu­(H₂O)­(2,2′-bpy)­(H₂L)]₂·H₄L·4H₂O (<b>1</b>), [{Cu­(H₂O)­(2,2′-bpy)­(H₃L)}₂(H₂L)]·2H₂O (<b>2</b>), [Cu­(H₂O)­(1,10-phen)­(H₂L)]₂·6H₂O (<b>3</b>), [Cu­(2,2′-bpy)­(H₂L)]_<i>n</i>·<i>n</i>H₂O (<b>4</b>), [Cu­(1,10-phen)­(H₂L)]_<i>n</i>·3<i>n</i>H₂O (<b>5</b>), and [{Cu­(2,2′-bpy)­(MoO₃)}₂(L)]_<i>n</i>·2<i>n</i>H₂O (<b>6</b>) have been synthesized starting from <i>p</i>-xylylenediphosphonic acid (H₄L) and 2,2′-bipyridine (2,2′-bpy) or 1,10-phenanthroline (1,10-phen) as secondary linkers and characterized by single crystal X-ray diffraction analysis, IR spectroscopy, and thermogravimetric (TG) analysis. All the complexes were synthesized by hydrothermal methods. A dinuclear motif (Cu-dimer) bridged by phosphonic acid represents a new class of simple building unit (SBU) in the construction of coordination architectures in metal phosphonate chemistry. The initial pH of the reaction mixture induced by the secondary linker plays an important role in the formation of the molecular phosphonates <b>1</b>, <b>2</b>, and <b>3</b>. Temperature dependent hydrothermal synthesis of the compounds <b>1</b>, <b>2</b>, and <b>3</b> reveals the mechanism of the self-assembly of the compounds based on the solubility of the phosphonic acid H₄L. Two-dimensional coordination polymers <b>4</b>, <b>5</b>, and <b>6</b>, which are formed by increasing the pH of the reaction mixture, comprise Cu-dimers as nodes, organic (H₂L) and inorganic (Mo₄O₁₂) ligands as linkers. The void space-areas, created by the (4,4) connected nets in compounds <b>4</b> and <b>5</b>, are occupied by lattice water molecules. Thus compounds <b>4</b> and <b>5</b> have the potential to accommodate guest species/molecules. Variable temperature magnetic studies of the compounds <b>3</b>, <b>4</b>, <b>5</b>, and <b>6</b> reveal the antiferromagnetic interactions between the two Cu­(II) ions in the eight-membered ring, observed in their crystal structures. A density functional theory (DFT) calculation correlates the conformation of the Cu-dimer ring with the magnitude of the exchange parameter based on the torsion angle of the conformation

Mechanistic Aspects for the Formation of Copper Dimer Bridged by Phosphonic Acid and Extending Its Dimensionality by Organic and Inorganic Linkers: Synthesis, Structural Characterization, Magnetic Properties, and Theoretical Studies

Six new copper metal complexes with formulas [Cu­(H₂O)­(2,2′-bpy)­(H₂L)]₂·H₄L·4H₂O (<b>1</b>), [{Cu­(H₂O)­(2,2′-bpy)­(H₃L)}₂(H₂L)]·2H₂O (<b>2</b>), [Cu­(H₂O)­(1,10-phen)­(H₂L)]₂·6H₂O (<b>3</b>), [Cu­(2,2′-bpy)­(H₂L)]_<i>n</i>·<i>n</i>H₂O (<b>4</b>), [Cu­(1,10-phen)­(H₂L)]_<i>n</i>·3<i>n</i>H₂O (<b>5</b>), and [{Cu­(2,2′-bpy)­(MoO₃)}₂(L)]_<i>n</i>·2<i>n</i>H₂O (<b>6</b>) have been synthesized starting from <i>p</i>-xylylenediphosphonic acid (H₄L) and 2,2′-bipyridine (2,2′-bpy) or 1,10-phenanthroline (1,10-phen) as secondary linkers and characterized by single crystal X-ray diffraction analysis, IR spectroscopy, and thermogravimetric (TG) analysis. All the complexes were synthesized by hydrothermal methods. A dinuclear motif (Cu-dimer) bridged by phosphonic acid represents a new class of simple building unit (SBU) in the construction of coordination architectures in metal phosphonate chemistry. The initial pH of the reaction mixture induced by the secondary linker plays an important role in the formation of the molecular phosphonates <b>1</b>, <b>2</b>, and <b>3</b>. Temperature dependent hydrothermal synthesis of the compounds <b>1</b>, <b>2</b>, and <b>3</b> reveals the mechanism of the self-assembly of the compounds based on the solubility of the phosphonic acid H₄L. Two-dimensional coordination polymers <b>4</b>, <b>5</b>, and <b>6</b>, which are formed by increasing the pH of the reaction mixture, comprise Cu-dimers as nodes, organic (H₂L) and inorganic (Mo₄O₁₂) ligands as linkers. The void space-areas, created by the (4,4) connected nets in compounds <b>4</b> and <b>5</b>, are occupied by lattice water molecules. Thus compounds <b>4</b> and <b>5</b> have the potential to accommodate guest species/molecules. Variable temperature magnetic studies of the compounds <b>3</b>, <b>4</b>, <b>5</b>, and <b>6</b> reveal the antiferromagnetic interactions between the two Cu­(II) ions in the eight-membered ring, observed in their crystal structures. A density functional theory (DFT) calculation correlates the conformation of the Cu-dimer ring with the magnitude of the exchange parameter based on the torsion angle of the conformation