Synthesis and Crystallization Behavior of Surfactants with Hexamolybdate as the Polar Headgroup

Alkyl chains with different lengths were covalently grafted onto the surface of hexamolybdate through the postfunctionalization protocol of polyoxometalates. The obtained compounds represent typical structures of the so-called giant surfactants. Unexpectedly, those surfactants with hexamolybdates as polar headgroups are able to crystallize, while single-crystal X-ray diffraction reveals that the crystallization behavior of the surfactants is highly dependent on the length of the alkyl chains. For surfactants with comparatively short alkyl chains (C6 and C10), the alkyl chains prefer to interact with tetrabutylammonium, the countercation of hexamolybdate. However, the alkyl chains tend to pack with each other to form a domain of alkyl chains in the surfactant with a longer alkyl chain (C18). The possible mechanism is that a long alkyl chain cannot be fully compatible with the short chain (C4) of tetrabutylammonium

Synthesis and Crystallization Behavior of Surfactants with Hexamolybdate as the Polar Headgroup

Alkyl chains with different lengths were covalently grafted onto the surface of hexamolybdate through the postfunctionalization protocol of polyoxometalates. The obtained compounds represent typical structures of the so-called giant surfactants. Unexpectedly, those surfactants with hexamolybdates as polar headgroups are able to crystallize, while single-crystal X-ray diffraction reveals that the crystallization behavior of the surfactants is highly dependent on the length of the alkyl chains. For surfactants with comparatively short alkyl chains (C6 and C10), the alkyl chains prefer to interact with tetrabutylammonium, the countercation of hexamolybdate. However, the alkyl chains tend to pack with each other to form a domain of alkyl chains in the surfactant with a longer alkyl chain (C18). The possible mechanism is that a long alkyl chain cannot be fully compatible with the short chain (C4) of tetrabutylammonium

Molecular Photocatalysts Based on Quinolinium-Grafted Polyoxometalates for Efficient One-Step Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids

Based on the need for green synthesis, photocatalytic oxidation reactions under ambient conditions are vitally significant. Herein, we developed six new quinolinium-grafted polyoxometalate (Q-POM) structures and explored their photocatalytic ability in the photocatalytic aerobic oxidation of benzyl alcohol-like compounds. Among them, (Bu4N)2+{AlMo6O18[(OCH2)3CCH3][(OCH2)3CNHCOCH2C9H7N]}2– (TBA-Q-Al) can achieve the one-step oxidation of various benzyl alcohols to the corresponding benzoic acid compounds with favorable yields under blue light irradiation at 420–430 nm accompanied by oxygen as the sole oxidant. The photocatalyst combines the ability of quinolinium π–π conjugation to respond to light and the property of the POM backbone to storage-transfer electrons. This work provides guidance for the subsequent development of more efficient quinolinium-grafted POM structures for photocatalytic conversions

Molecular Photocatalysts Based on Quinolinium-Grafted Polyoxometalates for Efficient One-Step Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids

Based on the need for green synthesis, photocatalytic oxidation reactions under ambient conditions are vitally significant. Herein, we developed six new quinolinium-grafted polyoxometalate (Q-POM) structures and explored their photocatalytic ability in the photocatalytic aerobic oxidation of benzyl alcohol-like compounds. Among them, (Bu4N)2+{AlMo6O18[(OCH2)3CCH3][(OCH2)3CNHCOCH2C9H7N]}2– (TBA-Q-Al) can achieve the one-step oxidation of various benzyl alcohols to the corresponding benzoic acid compounds with favorable yields under blue light irradiation at 420–430 nm accompanied by oxygen as the sole oxidant. The photocatalyst combines the ability of quinolinium π–π conjugation to respond to light and the property of the POM backbone to storage-transfer electrons. This work provides guidance for the subsequent development of more efficient quinolinium-grafted POM structures for photocatalytic conversions

Step-by-Step Strategy from Achiral Precursors to Polyoxometalates-Based Chiral Organic–Inorganic Hybrids

Using two types of triol ligands, several novel asymmetrically triol-functionalized Anderson organic hybrids have been efficiently synthesized in high purity and good yields via a convenient two-step esterification reaction. These organic–inorganic hybrids are chiral and can be spontaneously resolved with suitable solvents. Their molecular and crystal structures have been confirmed by single-crystal X-ray diffraction studies. Stable solid-state chirality of the corresponding enantiopure crystals has also been confirmed definitively by CD spectra. Interestingly, these organic–inorganic hybrids possess a layer-by-layer structure, forming solvent-accessible nanoscale chiral channels via a 1D infinite helical chain substructure. TGA measurements indicated that the species of the central heteroatoms significantly effects the stability of these compounds

A Series of Weakley-type Polyoxomolybdates: Synthesis, Characterization, and Magnetic Properties by a Combined Experimental and Theoretical Approach

Using DCC as the dehydrating agent, a series of Weakley-type polyoxomolybdates [Bu₄N]₃{Ln­[Mo₅O₁₃(OMe)₄(NO)]₂} (Ln = Tb, Dy, Ho, Er) were synthesized in a one-pot reaction and structurally characterized by elemental, IR, UV–vis analysis, PXRD, and single-crystal X-ray diffraction. Furthermore, the static and dynamic measurements were utilized to investigate their magnetic performances. Typically, slow relaxation of magnetization was observed for Dy analogues with an energy barrier for the reversal of the magnetization of 50 K, which is the highest barrier height observed on the polyoxomolybdates-based single-molecule magnets (SMMs). For a deep understanding of the appearance of the SMM behavior on Weakley-type polyoxomolybdates series, <i>ab initio</i> calculations on {Dy­[Mo₅O₁₃(OMe)₄(NO)]₂}^3– have been conducted

Organoimido-Derivatized Hexamolybdates with a Remote Carboxyl Group: Syntheses and Structural Characterizations

Four novel organoimido derivatives of hexamolybdate containing a remote carboxyl group have been synthesized: [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-3-COOH)] (<b>1</b>), [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-4-COOH)] (<b>2</b>), [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-5-COOH)] (<b>3</b>), and [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-3-COOH)] (<b>4</b>) with 3-aminobenzoic acid, 4-amino-3-methylbenzoic acid, 3-amino-4-methylbenzoic acid, and 3-amino-2-methylbenzoic acid as the imido-releasing agents, respectively. Their structures have been characterized by IR, UV–vis, ¹H NMR, ESI–MS, and single-crystal X-ray diffraction techniques. Hydrogen bonding interactions play an important role in the supramolecular assemblies of these compounds in the solid state. Although the incorporated organic ligands are similar to each other, their supramolecular assembly behaviors are quite different. For compound <b>1</b>, the dimer structure is formed via hydrogen bonding between the carboxyl group and the POM cluster of two neighboring cluster anions. For compound <b>2</b>, the 1D chain structure is formed via hydrogen bonding between the carboxyl groups and the POM clusters of the cluster anions. For compound <b>3</b>, the 2D plane structure is formed via two types of hydrogen bonding between the aromatic rings and the POM clusters of the cluster anions. For compound <b>4</b>, the 1D plus 2D structures are formed via three types of hydrogen bonding between the aromatic rings and the POM clusters of the two types of cluster anions with different orientations

Control of Intramolecular π–π Stacking Interaction in Cationic Iridium Complexes via Fluorination of Pendant Phenyl Rings

Intramolecular π–π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir­(ppy)₂(F2phpzpy)]­PF₆ (<b>2</b>) and [Ir­(ppy)₂(F5phpzpy)]­PF₆ (<b>3</b>), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir­(ppy)₂(phpzpy)]­PF₆ (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1<i>H</i>-pyrazol-3-yl)­pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1<i>H</i>-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1<i>H</i>-pyrazol-3-yl)­pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes <b>1</b>, <b>2</b>, and <b>3</b>, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 Å for complexes <b>1</b>, <b>2</b>, and <b>3</b>, respectively, indicating progressively reinforced intramolecular π–π stacking interactions from complexes <b>1</b> to <b>2</b> and <b>3</b>. Compared to complex <b>1</b>, complex <b>3</b> with a significantly reinforced intramolecular face-to-face π–π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex <b>3</b> it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π–π stacking interaction remains on the lowest triplet state

Organoimido-Derivatized Hexamolybdates with a Remote Carboxyl Group: Syntheses and Structural Characterizations

Four novel organoimido derivatives of hexamolybdate containing a remote carboxyl group have been synthesized: [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-3-COOH)] (<b>1</b>), [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-4-COOH)] (<b>2</b>), [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-5-COOH)] (<b>3</b>), and [Bu₄N]₂[Mo₆O₁₈(N-C₆H₄-2-CH₃-3-COOH)] (<b>4</b>) with 3-aminobenzoic acid, 4-amino-3-methylbenzoic acid, 3-amino-4-methylbenzoic acid, and 3-amino-2-methylbenzoic acid as the imido-releasing agents, respectively. Their structures have been characterized by IR, UV–vis, ¹H NMR, ESI–MS, and single-crystal X-ray diffraction techniques. Hydrogen bonding interactions play an important role in the supramolecular assemblies of these compounds in the solid state. Although the incorporated organic ligands are similar to each other, their supramolecular assembly behaviors are quite different. For compound <b>1</b>, the dimer structure is formed via hydrogen bonding between the carboxyl group and the POM cluster of two neighboring cluster anions. For compound <b>2</b>, the 1D chain structure is formed via hydrogen bonding between the carboxyl groups and the POM clusters of the cluster anions. For compound <b>3</b>, the 2D plane structure is formed via two types of hydrogen bonding between the aromatic rings and the POM clusters of the cluster anions. For compound <b>4</b>, the 1D plus 2D structures are formed via three types of hydrogen bonding between the aromatic rings and the POM clusters of the two types of cluster anions with different orientations

Control of Intramolecular π–π Stacking Interaction in Cationic Iridium Complexes via Fluorination of Pendant Phenyl Rings

Intramolecular π–π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir­(ppy)₂(F2phpzpy)]­PF₆ (<b>2</b>) and [Ir­(ppy)₂(F5phpzpy)]­PF₆ (<b>3</b>), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir­(ppy)₂(phpzpy)]­PF₆ (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1<i>H</i>-pyrazol-3-yl)­pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1<i>H</i>-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1<i>H</i>-pyrazol-3-yl)­pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes <b>1</b>, <b>2</b>, and <b>3</b>, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 Å for complexes <b>1</b>, <b>2</b>, and <b>3</b>, respectively, indicating progressively reinforced intramolecular π–π stacking interactions from complexes <b>1</b> to <b>2</b> and <b>3</b>. Compared to complex <b>1</b>, complex <b>3</b> with a significantly reinforced intramolecular face-to-face π–π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex <b>3</b> it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π–π stacking interaction remains on the lowest triplet state