Cadmium Metal–Organic Frameworks Based on Ditopic Triazamacrocyclic Linkers: Unusual Structural Features and Selective CO₂ Capture

Two three-dimensional cadmium metal–organic frameworks with general formula [Cd₂(<b>L</b>^<b>1</b>)­(H₂O)₃]­(NO₃)_0.7­(HCOO)_0.2Br_0.1 (<b>Cd</b>_<b>2</b><b>L</b>^<b>1</b>, <b>L</b>^<b>1</b> = 1,4,7-tris­(4-carboxybenzyl)-1,4,7-triazacyclononane) and Cd­(<b>HL</b>^<b>2</b>)­(H₂O)₂ (<b>CdL</b>^<b>2</b>, <b>L</b>^<b>2</b> = 1,4,7-tris­(3-(4-benzoate)­prop-2-yn-1-yl)-1,4,7-triazacyclononane) based on 1,4,7-triazacyclononane <i>N</i>-functionalized by different arylcarboxylic acids were prepared under solvothermal conditions and characterized by single crystal X-ray analysis and porosity measurements. The crystal structure of <b>Cd</b>_<b>2</b><b>L</b>^<b>1</b> reveals a cationic net with a <i>bcs</i> topology, and nodes are constituted by dinuclear cadmium complexes, in which each cadmium atom adopts a hexacoordinated environment involving both the carboxylate and the cyclic amine. In contrast, <b>CdL</b>^<b>2</b> displays a 2-fold interpenetrated structure with a <i>pcu</i> topology. In this net, the node is a mononuclear complex in which the Cd atom exhibits a seven-coordination geometry. Both materials show a high permanent porosity and good CO₂ adsorption properties with a high selectivity over N₂ and CH₄. The adsorption capacity and selectivity for CO₂ were calculated from a multisite Langmuir isotherm model and the ideal adsorbed solution theory, which gave insights into the nature of solid–gas interactions and showed the influence of interpenetration or polarity of the charged framework on their adsorption properties

<i>o</i>‑(Hydroxyalkyl)phenyl P‑Chirogenic Phosphines as Functional Chiral Lewis Bases

The stereoselective synthesis of P-chirogenic phosphines bearing an <i>o</i>-hydroxyalkyl chelating arm is described. The synthesis is based either on the hydroxyalkylation of P-chirogenic <i>o</i>-bromophenylphosphines (borane) or on their carbonatation and then reduction. The hydroxyalkylation with benzaldehyde or pivalaldehyde affords a mixture of epimers which are isolated by chromatography and characterized by their X-ray structures. Preliminary assays of free P-chirogenic <i>o</i>-(hydroxyalkyl)phenyl phosphines, as new functional Lewis bases in catalyzed asymmetric aza-MBH reaction, lead to β-aminoester derivatives with ee values up to 74%

A Comparative IRMPD and DFT Study of Fe³⁺ and UO₂²⁺ Complexation with <i>N</i>‑Methylacetohydroxamic Acid

Iron­(III) and uranyl complexes of <i>N</i>-methylacetohydroxamic acid (NMAH) have been investigated by mass spectrometry, infrared multiphoton dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. A comparison between IRMPD and theoretical IR spectra enabled one to probe the structures for some selected complexes detected in the gas phase. The results show that coordination of Fe³⁺ and UO₂²⁺ by hydroxamic acid is of a very similar nature. Natural bond orbital analysis suggests that bonding in uranyl complexes possesses a slightly stronger ionic character than that in iron complexes. Collision-induced dissociation (CID), IRMPD, and ¹⁸O-labeling experiments unambiguously revealed a rare example of the UO bond activation concomitant with the elimination of a water molecule from the gaseous [UO₂(NMA)­(NMAH)₂]⁺ complex. The UO bond activation is observed only for complexes with one monodentate NMAH molecule forming a hydrogen bond toward one “yl” oxygen atom, as was found by DFT calculations. This reactivity might explain oxygen exchange observed for uranyl complexes

<i>o</i>‑(Hydroxyalkyl)phenyl P‑Chirogenic Phosphines as Functional Chiral Lewis Bases

The stereoselective synthesis of P-chirogenic phosphines bearing an <i>o</i>-hydroxyalkyl chelating arm is described. The synthesis is based either on the hydroxyalkylation of P-chirogenic <i>o</i>-bromophenylphosphines (borane) or on their carbonatation and then reduction. The hydroxyalkylation with benzaldehyde or pivalaldehyde affords a mixture of epimers which are isolated by chromatography and characterized by their X-ray structures. Preliminary assays of free P-chirogenic <i>o</i>-(hydroxyalkyl)phenyl phosphines, as new functional Lewis bases in catalyzed asymmetric aza-MBH reaction, lead to β-aminoester derivatives with ee values up to 74%

Modular <i>P</i>‑Chirogenic Phosphine-Sulfide Ligands: Clear Evidence for Both Electronic Effect and <i>P</i>‑Chirality Driving Enantioselectivity in Palladium-Catalyzed Allylations

Using the ephedrine methodology, modular stereoselective syntheses of a new class of <i>P</i>-chirogenic phosphines bearing a sulfur-chelating arm (P*,S-hybrid ligand) are described. A first series of syntheses based on a Fries-like rearrangement of <i>P</i>-chirogenic phosphinite-boranes, which are prepared from 2-bromobenzyl or 2-bromophenethyl alcohol and are mediated by metal–halide exchange, have been performed. This rearrangement affords phosphine-boranes stereospecifically with an <i>o</i>-hydroxy­alkylphenyl substituent. The latter residue is subsequently converted into a sulfur-containing group. In a second series, the stereoselective syntheses were achieved according to a new strategy involving a reaction of a thiophenyllithium reagent with a <i>P</i>-chirogenic phosphinite. The X-ray structures of the P*,S ligands and their palladium complexes allow us to address the absolute configuration at both the phosphorus and sulfur centers. The P*,S ligands were used in palladium-catalyzed allylic alkylations, as tests, affording asymmetric inductions up to 96% ee. Computer modeling corroborates the regio- and enantioselectivity of the Pd-catalyzed allylations and the low influence of the substituent carried by the sulfur moiety, particularly when the chelate forms a six-membered ring with the metal

Efficient Synthesis of (P-Chirogenic) <i>o</i>‑Boronated Phosphines from <i>sec</i>-Phosphine Boranes

An efficient synthesis of boronated phosphines with an <i>o</i>-phenylene-bridge prepared from <i>sec</i>-phosphine boranes and using benzyne chemistry is reported. Successive reactions of <i>sec</i>-phosphine boranes with <i>n</i>-BuLi and 1,2-dibromobenzene, and then with boron reagents, afford the <i>o</i>-boronato­phenyl­phosphine derivatives in 71% yields. The use of P-chirogenic <i>sec</i>-phosphine boranes leads to the free boronated phosphines with retention of configuration at the P-center after decomplexation. The reaction of P-chirogenic <i>o</i>-boronato­phenyl­phosphine with KHF₂ affords the corresponding trifluoroborated phosphine with ee >98%

Remarkable Inertness of Copper(II) Chelates of Cyclen-Based Macrobicycles with Two <i>trans</i>-<i>N</i>‑Acetate Arms

Two cross-bridged cyclen-based macrocycles with two <i>trans</i>-<i>N</i>-acetic acid arms, one having a dibenzofuran (DBF) moiety as the bridge, H₂L1, and the other a diphenyl ether (DPE) one, H₂L2, were synthesized. Both compounds behave as “proton sponges.” The thermodynamic stability constants for the Cu²⁺, Zn²⁺, Al³⁺, and Ga³⁺ complexes of both compounds were determined. They exhibit an excellent thermodynamic selectivity for copper­(II), ensuring that metal ions largely present in the human body do not interfere with the copper­(II) chelates. All complexes are very slow to form, and [CuL2] and [CuL1] are extremely inert to demetallate, especially [CuL2]. The acid-assisted dissociation of [CuL1] led to a half-life of 4.28 h in 5 M HCl at 363.2 K, while [CuL2] needed harsher conditions of 12 M HCl at 363.2 K with a half-life of 30.8 days. To the best of our knowledge, [CuL2] exhibits the highest half-life value for a copper­(II) complex of a polyazamacrocycle derivative reported in the literature until now. Single crystal X-ray diffraction determined for [Cu­(H₂L1)]­(ClO₄)₂ showed the copper center in a distorted octahedral environment bound to the N₄O donors of the macrobicycle and one oxygen atom from a carboxylic arm, while for [CuL2] it showed the copper center in a trigonal bipyramid geometry only bound to the donors of the macrobicycle and leaving the carboxylate arms away from the coordination sphere. UV–vis–NIR and X-band EPR spectra showed that in [CuL1] the copper center adopts a distorted compressed octahedral environment, which is the only structure found in solution for this complex, while in [CuL2] a similar environment was found in the first stages of its slow formation but reached a square-pyramidal geometry upon stabilization. The acetate arms play therefore an important role during the formation of the complex, as revealed by the comparison of its complexation behavior with the corresponding parent compounds

Remarkable Inertness of Copper(II) Chelates of Cyclen-Based Macrobicycles with Two <i>trans</i>-<i>N</i>‑Acetate Arms

Two cross-bridged cyclen-based macrocycles with two <i>trans</i>-<i>N</i>-acetic acid arms, one having a dibenzofuran (DBF) moiety as the bridge, H₂L1, and the other a diphenyl ether (DPE) one, H₂L2, were synthesized. Both compounds behave as “proton sponges.” The thermodynamic stability constants for the Cu²⁺, Zn²⁺, Al³⁺, and Ga³⁺ complexes of both compounds were determined. They exhibit an excellent thermodynamic selectivity for copper­(II), ensuring that metal ions largely present in the human body do not interfere with the copper­(II) chelates. All complexes are very slow to form, and [CuL2] and [CuL1] are extremely inert to demetallate, especially [CuL2]. The acid-assisted dissociation of [CuL1] led to a half-life of 4.28 h in 5 M HCl at 363.2 K, while [CuL2] needed harsher conditions of 12 M HCl at 363.2 K with a half-life of 30.8 days. To the best of our knowledge, [CuL2] exhibits the highest half-life value for a copper­(II) complex of a polyazamacrocycle derivative reported in the literature until now. Single crystal X-ray diffraction determined for [Cu­(H₂L1)]­(ClO₄)₂ showed the copper center in a distorted octahedral environment bound to the N₄O donors of the macrobicycle and one oxygen atom from a carboxylic arm, while for [CuL2] it showed the copper center in a trigonal bipyramid geometry only bound to the donors of the macrobicycle and leaving the carboxylate arms away from the coordination sphere. UV–vis–NIR and X-band EPR spectra showed that in [CuL1] the copper center adopts a distorted compressed octahedral environment, which is the only structure found in solution for this complex, while in [CuL2] a similar environment was found in the first stages of its slow formation but reached a square-pyramidal geometry upon stabilization. The acetate arms play therefore an important role during the formation of the complex, as revealed by the comparison of its complexation behavior with the corresponding parent compounds

Remarkable Inertness of Copper(II) Chelates of Cyclen-Based Macrobicycles with Two <i>trans</i>-<i>N</i>‑Acetate Arms

Two cross-bridged cyclen-based macrocycles with two <i>trans</i>-<i>N</i>-acetic acid arms, one having a dibenzofuran (DBF) moiety as the bridge, H₂L1, and the other a diphenyl ether (DPE) one, H₂L2, were synthesized. Both compounds behave as “proton sponges.” The thermodynamic stability constants for the Cu²⁺, Zn²⁺, Al³⁺, and Ga³⁺ complexes of both compounds were determined. They exhibit an excellent thermodynamic selectivity for copper­(II), ensuring that metal ions largely present in the human body do not interfere with the copper­(II) chelates. All complexes are very slow to form, and [CuL2] and [CuL1] are extremely inert to demetallate, especially [CuL2]. The acid-assisted dissociation of [CuL1] led to a half-life of 4.28 h in 5 M HCl at 363.2 K, while [CuL2] needed harsher conditions of 12 M HCl at 363.2 K with a half-life of 30.8 days. To the best of our knowledge, [CuL2] exhibits the highest half-life value for a copper­(II) complex of a polyazamacrocycle derivative reported in the literature until now. Single crystal X-ray diffraction determined for [Cu­(H₂L1)]­(ClO₄)₂ showed the copper center in a distorted octahedral environment bound to the N₄O donors of the macrobicycle and one oxygen atom from a carboxylic arm, while for [CuL2] it showed the copper center in a trigonal bipyramid geometry only bound to the donors of the macrobicycle and leaving the carboxylate arms away from the coordination sphere. UV–vis–NIR and X-band EPR spectra showed that in [CuL1] the copper center adopts a distorted compressed octahedral environment, which is the only structure found in solution for this complex, while in [CuL2] a similar environment was found in the first stages of its slow formation but reached a square-pyramidal geometry upon stabilization. The acetate arms play therefore an important role during the formation of the complex, as revealed by the comparison of its complexation behavior with the corresponding parent compounds

Reactivity of CuI and CuBr toward Dialkyl Sulfides RSR: From Discrete Molecular Cu₄I₄S₄ and Cu₈I₈S₆ Clusters to Luminescent Copper(I) Coordination Polymers

The 1D coordination polymer (CP) [(Me₂S)₃{Cu₂(μ-I)₂}]_<i>n</i> (<b>1</b>) is formed when CuI reacts with SMe₂ in <i>n</i>-heptane, whereas in acetonitrile (MeCN), the reaction forms exclusively the 2D CP [(Me₂S)₃{Cu₄(μ-I)₄}]_<i>n</i> (<b>2</b>) containing “flower-basket” Cu₄I₄ units. The reaction product of CuI with MeSEt is also solvent-dependent, where the 1D polymer [(MeSEt)₂{Cu₄(μ₃-I)₂(μ₂-I)₂}­(MeCN)₂]_<i>n</i> (<b>3</b>) containing “stepped-cubane” Cu₄I₄ units is isolated in MeCN. In contrast, the reaction in <i>n</i>-heptane affords the 1D CP [(MeSEt)₃{Cu₄(μ₃-I)₄}]_<i>n</i> (<b>4</b>) containing “closed-cubane” Cu₄I₄ clusters. The reaction of MeSPr with CuI provides the structurally related 1D CP [(MeSPr)₃{Cu₄(μ₃-I)₄}]_<i>n</i> (<b>5</b>), for which the X-ray structure has been determined at 115, 155, 195, 235, and 275 K, addressing the evolution of the metric parameters. Similarly to <b>4</b> and the previously reported CP [(Et₂S)₃{Cu₄(μ₃-I)₄}]_<i>n</i> (<i>Inorg. Chem.</i> <b>2010</b>, <i>49</i>, 5834), the 1D chain is built upon closed cubanes Cu₄(μ₃-I)₄ as secondary building units (SBUs) interconnected via μ-MeSPr ligands. The 0D tetranuclear clusters [(L)₄{Cu₄(μ₃-I)₄}] [L = EtSPr (<b>6</b>), Pr₂S (<b>7</b>)] respectively result from the reaction of CuI with EtSPr and <i>n</i>-Pr₂S. With <i>i</i>-Pr₂S, the octanuclear cluster [(<i>i</i>-Pr₂S)₆{Cu₈(μ₃-I)₃}­(μ₄-I)₂}] (<b>8</b>) is formed. An X-ray study has also been performed at five different temperatures for the 2D polymer [(Cu₃Br₃)­(MeSEt)₃]_<i>n</i> (<b>9</b>) formed from the reaction between CuBr and MeSEt in heptane. The unprecedented framework of <b>9</b> consists of layers with alternating Cu­(μ₂-Br)₂Cu rhomboids, which are connected through two μ-MeSEt ligands to tetranuclear open-cubane Cu₄Br₄ SBUs. MeSPr forms with CuBr in heptane the 1D CP [(Cu₃Br₃)­(MeSPr)₃]_<i>n</i> (<b>10</b>), which is converted to a 2D metal–organic framework [(Cu₅Br₅)­(μ₂-MeSPr)₃]_<i>n</i> (<b>11</b>) incorporating pentanuclear [(Cu₅(μ₄-Br)­(μ₂-Br)] SBUs when recrystallized in MeCN. The thermal stability and photophysical properties of these materials are also reported