Tandem Diels−Alder Cycloadditions of 2-Pyrone-5-acrylates for the Efficient Synthesis of Novel Tetracyclolactones

Readily prepared from the regioselective Pd-catalyzed coupling reactions of 3,5-dibromo-2-pyrone, 3-bromo-2-pyrone-5-carboxylates undergo tandem uninterrupted sequential Diels−Alder cycloaddition reactions with allyl vinyl ethers in a highly regio- and stereoselective fashion to provide a series of novel tetracyclolactones in good yields

Tandem Diels−Alder Cycloadditions of 2-Pyrone-5-acrylates for the Efficient Synthesis of Novel Tetracyclolactones

Readily prepared from the regioselective Pd-catalyzed coupling reactions of 3,5-dibromo-2-pyrone, 3-bromo-2-pyrone-5-carboxylates undergo tandem uninterrupted sequential Diels−Alder cycloaddition reactions with allyl vinyl ethers in a highly regio- and stereoselective fashion to provide a series of novel tetracyclolactones in good yields

A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd2(pzdc)2L(H2O)2]·5(H2O)·(CH3CH2OH)}n (1, H2pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, [Cd2(pzdc)2L]n, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO2 (195 K) over N2 (77 K) and O2 (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles

Fragments

Stepwise synthesis and structural characterization of one-dimensional coordination polymers whose topologies depend on the anions are reported. A simple ladder-type precursor, {[Ag₂(<b>L</b>)₂]­(ClO₄)₂}_<i>n</i> (<b>1</b>), was prepared by the reaction of bis­(4-pyridylmethyl)­sulfide (<b>L</b>) with AgClO₄. Treatment of <b>1</b> with potassium thiocyanate and potassium cyanide afforded a twisted ribbon-type chain of type [Ag­(<b>L</b>)­SCN]_<i>n</i> (<b>2</b>) and a triple-rail ladder of type [Ag₃(<b>L</b>)₂(CN)₃]_<i>n</i> (<b>3</b>), respectively. The result demonstrates that replacement of the noncoordinated perchlorate anions by pseudohalide ions in the coordination sphere of <b>1</b> plays a crucial role in determining the structures of the resulting species

A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd2(pzdc)2L(H2O)2]·5(H2O)·(CH3CH2OH)}n (1, H2pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, [Cd2(pzdc)2L]n, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO2 (195 K) over N2 (77 K) and O2 (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles

A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd2(pzdc)2L(H2O)2]·5(H2O)·(CH3CH2OH)}n (1, H2pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, [Cd2(pzdc)2L]n, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO2 (195 K) over N2 (77 K) and O2 (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles

A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd2(pzdc)2L(H2O)2]·5(H2O)·(CH3CH2OH)}n (1, H2pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, [Cd2(pzdc)2L]n, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO2 (195 K) over N2 (77 K) and O2 (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles

A Pillared-Layer Coordination Polymer with a Rotatable Pillar Acting as a Molecular Gate for Guest Molecules

The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd2(pzdc)2L(H2O)2]·5(H2O)·(CH3CH2OH)}n (1, H2pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, [Cd2(pzdc)2L]n, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO2 (195 K) over N2 (77 K) and O2 (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles

Soft Secondary Building Unit: Dynamic Bond Rearrangement on Multinuclear Core of Porous Coordination Polymers in Gas Media

A new synthetic approach to prepare flexible porous coordination polymers (PCPs) by the use of soft secondary building units (SBUs) which can undergo multiple reversible metal–ligand bonds breaking is reported. We have prepared a zinc paddle-wheel-based two-fold interpenetrated PCP, {[Zn2(tp)2(L2)]·2.5DMF·0.5water}n (2a, H2tp = terephthanlic acid; L2 = 2,3-difluoro-1,4-bis(4-pyridyl)benzene), showing dynamic structural transformations upon the removal and rebinding of guest molecules. The X-ray structures at different degrees of desolvation indicate the highly flexible nature of the framework. The framework deformations involve slippage of the layers and movement of the two interpenetrated frameworks with respect to each other. Interestingly, the coordination geometry of a zinc paddle-wheel unit (one of the popular SBUs) is considerably changed by bond breaking between zinc and oxygen atoms during the drying process. Two zinc atoms in the dried form 2d reside in a distorted tetrahedral geometry. Compound 2d has no void volume and favors the uptake of O2 over Ar and N2 at 77 K. The O2 and Ar adsorption isotherms of 2d show gate-opening-type adsorption behaviors corroborating the structure determination. The CO2 adsorption isotherm at 195 K exhibits multiple steps originating from the flexibility of the framework. The structural transformations of the zinc clusters in the framework upon sorption of guest molecules are also characterized by Raman spectroscopy in which the characteristic bands corresponding to νsym(COO–) vibration were used

Stepwise Synthesis of Charged and Neutral Two-Dimensional Networks via One-Dimensional Silver(I) Coordination Polymer Based on Bis(4-pyridylmethyl)sulfide

Stepwise synthesis and structural characterization of two-dimensional (2-D) coordination polymer frameworks with positive charged or neutral cavities are reported. First, reactions of bis(4-pyridylmethyl)sulfide (L) with silver salts (1: nitrate and 2: perchlorate) afforded the respective double-stranded one-dimensional (1-D) chains [Ag(L)NO3]n (1) and {[Ag2(L)2](ClO4)2}n (2), both of which are stabilized by face-to-face π−π interactions. In this case, the silver(I) center in the nitrato complex 1 shows four-coordinated distorted tetrahedral geometry, whereas that of the perchlorato complex 2 exhibits a distorted trigonal planar geometry. The difference of these structures indicates that the coordination ability of the anions has important effects on the silver(I) coordination environments. Interestingly, the perchlorato 1-D complex 2 allows further reactions with bridging ligands such as 4,4′-bipyridine (bpy) and terephthalate (tp2−) to give a 2-D positive-charged network {[Ag2(L)2(bpy)]·(ClO4)2·C6H6}n (3) and a 2-D neutral network {[Ag2(L)2(tp)]·2DMSO·6H2O}n (4), respectively. The nitrato 1-D complex 1, however, showed no reactivity with the bridging ligands in the same condition. The results show that the replacement of anion by the bridging ligand in the coordination sphere of the 1-D precursor plays crucial roles in determining the reactivity for the synthesis of higher dimensional open frameworks