Self-Assembly of Molecular Nanoball: Design, Synthesis, and Characterization

The design and self-assembly of two new flexible supramolecular nanoballs are described. These assemblies incorporate two flexible tritopic amide and ester building blocks and were prepared in excellent yields (96−97%) via coordination driven self-assembly. The first resulted from the reaction of 4 equiv of a new tritopic ester ligand N,N‘,N‘ ‘-tris(4-pyridylmethyl) trimesic ester and 3 equiv of C4 symmetric Pd(NO3)2. The second analogous structure was obtained by the self-assembly of a flexible N,N‘,N‘ ‘-tris(3-pyridylmethyl) trimesic amide and Pd(NO3)2. The assemblies were characterized with multinuclear NMR spectroscopy, electrospray ionization mass spectroscopy, elemental analysis, and TGA. Mass spectrometry along with NMR data and TEM view confirms the existence of the two assemblies. MM2 force field simulations of the cages showed a ball shape with the diameter of the inner cavity of about 2.1 and 1.8 nm for 2a and 2b, respectively, which were also corroborated by TEM analysis

Self-Assembly of a Nanoscopic Prism via a New Organometallic Pt₃ Acceptor and Its Fluorescent Detection of Nitroaromatics

A nanoscale-sized cage with a trigonal prismatic shape is prepared by coordination-driven self-assembly of a predesigned organometallic Pt3 acceptor with an organic clip-type ligand. This trigonal prism is fluorescent and undergoes efficient fluorescence quenching by nitroaromatics, which are the chemical signatures of many explosives

Self-Assembly of a Nanoscopic Prism via a New Organometallic Pt₃ Acceptor and Its Fluorescent Detection of Nitroaromatics

A nanoscale-sized cage with a trigonal prismatic shape is prepared by coordination-driven self-assembly of a predesigned organometallic Pt3 acceptor with an organic clip-type ligand. This trigonal prism is fluorescent and undergoes efficient fluorescence quenching by nitroaromatics, which are the chemical signatures of many explosives

Self-Assembled Pd(II) Metallocycles Using an Ambidentate Donor and the Study of Square−Triangle Equilibria

The self-assembly reaction of a cis-blocked 90° square planar metal acceptor with a symmetrical linear flexible linker is expected to yield a [4 + 4] self-assembled square, a [3 + 3] assembled triangle, or a mixture of these. However, if the ligand is a nonsymmetrical ambidentate, it is expected to form a complex mixture comprising several linkage isomeric squares and triangles as a result of different connectivities of the ambidentate linker. We report instead that the reaction of a 90° acceptor cis-(dppf)Pd(OTf)2 [where dppf = 1,1′-bis(diphenylphosphino)ferrocene] with an equimolar amount of the ambidentate unsymmetrical ligand Na-isonicotinate unexpectedly yields a mixture of symmetrical triangles and squares in the solution. An analogous reaction using cis-(tmen)Pd(NO3)2 instead of cis-(dppf)Pd(OTf)2 also produced a mixture of symmetrical triangles and squares in the solution. In both cases the square was isolated as the sole product in the solid state, which was characterized by a single crystal structure analysis. The equilibrium between the triangle and the square in the solution is governed by the enthalpic and entropic contributions. The former parameter favors the formation of the square due to less strain in the structure whereas the latter one favors the formation of triangles due to the formation of more triangles from the same number of starting linkers. The effects of temperature and concentration on the equilibria have been studied by NMR techniques. This represents the first report on the study of square-triangle equilibria obtained using a nonsymmetric ambidentate linker. Detail NMR spectroscopy along with the ESI−mass spectrometry unambiguously identified the components in the mixture while the X-ray structure analysis determined the solid-state structure

Self-Assembled Pd(II) Metallocycles Using an Ambidentate Donor and the Study of Square−Triangle Equilibria

The self-assembly reaction of a cis-blocked 90° square planar metal acceptor with a symmetrical linear flexible linker is expected to yield a [4 + 4] self-assembled square, a [3 + 3] assembled triangle, or a mixture of these. However, if the ligand is a nonsymmetrical ambidentate, it is expected to form a complex mixture comprising several linkage isomeric squares and triangles as a result of different connectivities of the ambidentate linker. We report instead that the reaction of a 90° acceptor cis-(dppf)Pd(OTf)2 [where dppf = 1,1′-bis(diphenylphosphino)ferrocene] with an equimolar amount of the ambidentate unsymmetrical ligand Na-isonicotinate unexpectedly yields a mixture of symmetrical triangles and squares in the solution. An analogous reaction using cis-(tmen)Pd(NO3)2 instead of cis-(dppf)Pd(OTf)2 also produced a mixture of symmetrical triangles and squares in the solution. In both cases the square was isolated as the sole product in the solid state, which was characterized by a single crystal structure analysis. The equilibrium between the triangle and the square in the solution is governed by the enthalpic and entropic contributions. The former parameter favors the formation of the square due to less strain in the structure whereas the latter one favors the formation of triangles due to the formation of more triangles from the same number of starting linkers. The effects of temperature and concentration on the equilibria have been studied by NMR techniques. This represents the first report on the study of square-triangle equilibria obtained using a nonsymmetric ambidentate linker. Detail NMR spectroscopy along with the ESI−mass spectrometry unambiguously identified the components in the mixture while the X-ray structure analysis determined the solid-state structure

Self-Assembly of Metallamacrocycles via a Rigid Phosphorus Donor Linker^#

The coordination-driven self-assembly of a series of discrete 2D metallomacrocycles from a rigid diphosphine donor linker and Pd/Pt-containing 90° acceptors is described. All these assemblies are characterized by multinuclear NMR and, in four cases, X-ray crystallography. The selective formation of a diphosphine bridged macrocycle, [(en)Pd(μ-trans-PPh2CHCHPPh2)2Pd(en)]4+, from a 1:1:1 mixture of cis-Pd(en)(NO3)2, trans-Ph2PCHCHPPh2, and 1,2-bis(4-pyridyl)ethane is also established

Self-Assembly of Metallamacrocycles via a Rigid Phosphorus Donor Linker^#

The coordination-driven self-assembly of a series of discrete 2D metallomacrocycles from a rigid diphosphine donor linker and Pd/Pt-containing 90° acceptors is described. All these assemblies are characterized by multinuclear NMR and, in four cases, X-ray crystallography. The selective formation of a diphosphine bridged macrocycle, [(en)Pd(μ-trans-PPh2CHCHPPh2)2Pd(en)]4+, from a 1:1:1 mixture of cis-Pd(en)(NO3)2, trans-Ph2PCHCHPPh2, and 1,2-bis(4-pyridyl)ethane is also established

Design, Synthesis, and Characterizations of a Series of Pt₄ Macrocycles and Fluorescent Sensing of Fe³⁺/Cu²⁺/Ni²⁺ Through Metal Coordination

A PtII2 organometallic “clip” (1a) containing ethynyl functionality is synthesized. Multinuclear NMR and electrospray ionization mass spectrometry characterized this “clip”, and the molecular structure was determined in an X-ray single-crystal diffraction study. A series of discrete molecular rectangles (2a−d) have been synthesized from this “clip” in combination with dipyridyl-based linear linkers (L1−4) by a metal−ligand coordination driven self-assembly approach [where L1 = 4,4′-bipyridine, L2 = trans-1,2-bis(4-pyridyl)ethylene, L3 = N-(4-pyridyl)isonicotinamide, and L4 = N,N′-bis(4-pyridylidene)ethylenediamine]. Rectangle 2d was designed using the imine-based ligand L4 to make it a system composed of a fluorophore−receptor−fluorophore combination. The imine N4 pocket is the receptor site, while the anthracene-based “clip” is the fluorophore. Complex 2d is fluorescent in nature and showed fluorescence quenching in solution upon the binding of hard transition metal ions (Fe3+, Cu2+, Ni2+, and Mn2+) into the N4 pocket. The nonresponsive nature of the fluorescence intensity upon the addition of soft metal ions (Zn2+ and Cd2+) having d10 configuration makes it a suitable sensor for transition metal ions. The fluorescence intensity of the Ni2+ bound complex was regained when the metal was removed by a stronger chelating 2,2′-dipyridyl ligand

Design, Synthesis, and Characterizations of a Series of Pt₄ Macrocycles and Fluorescent Sensing of Fe³⁺/Cu²⁺/Ni²⁺ Through Metal Coordination

A PtII2 organometallic “clip” (1a) containing ethynyl functionality is synthesized. Multinuclear NMR and electrospray ionization mass spectrometry characterized this “clip”, and the molecular structure was determined in an X-ray single-crystal diffraction study. A series of discrete molecular rectangles (2a−d) have been synthesized from this “clip” in combination with dipyridyl-based linear linkers (L1−4) by a metal−ligand coordination driven self-assembly approach [where L1 = 4,4′-bipyridine, L2 = trans-1,2-bis(4-pyridyl)ethylene, L3 = N-(4-pyridyl)isonicotinamide, and L4 = N,N′-bis(4-pyridylidene)ethylenediamine]. Rectangle 2d was designed using the imine-based ligand L4 to make it a system composed of a fluorophore−receptor−fluorophore combination. The imine N4 pocket is the receptor site, while the anthracene-based “clip” is the fluorophore. Complex 2d is fluorescent in nature and showed fluorescence quenching in solution upon the binding of hard transition metal ions (Fe3+, Cu2+, Ni2+, and Mn2+) into the N4 pocket. The nonresponsive nature of the fluorescence intensity upon the addition of soft metal ions (Zn2+ and Cd2+) having d10 configuration makes it a suitable sensor for transition metal ions. The fluorescence intensity of the Ni2+ bound complex was regained when the metal was removed by a stronger chelating 2,2′-dipyridyl ligand

Green Synthesis of Novel Polyesterurethane Materials from Epoxides and Carbon Dioxide by New Set of One-Dimensional Coordination Polymer Catalyst

Two novel polyesterurethane materials, PEU1 and PEU2, were synthesized via nontoxic and isocyanate-free route by simple conversion of two epoxides 1,2-epoxy-3-phenoxy propane (2) and styrene epoxide (3) utilizing CO2. Epoxides 2 and 3 were converted to the respective cyclic carbonates 4 and 5 by a new set of cobalt-based catalyst 1a in the presence of 10 bar of CO2 and 80 °C temperature without using cocatalyst tetrabutylammonium bromide (TBAB). The mechanistic pathway of the catalysis reaction for the cycloaddition of epoxides with CO2 to generate the cyclic carbonates was investigated by several spectroscopic techniques and utilizing analogous zinc-based 1D coordination polymer 1b, which does not act as an efficient catalyst in the absence of TBAB. Cyclic carbonates 4 and 5 were converted to the respective polyesterurethanes PEU1 and PEU2 sequentially by first synthesizing the ring-opened diols 6 and 7 reacting with ethylenediamine and subsequently annealing the respective diols 6 and 7 at 120 °C in the presence of terepthalyl chloride and triethylamine. The polyesterurethanes PEU1 and PEU2 were characterized by multinuclear NMR and FTIR. PEU1 was also characterized by MALDI-TOF mass spectrometry. The thermal studies of PEU1 and PEU2 showed the stability up to 200–270 °C. The number-average and weight-average molecular weights were determined for PEU1 and PEU2 by GPC analysis. The weight-average molecular weight for PEU1 was found to be 5948 with a polydispersity of 1.1, and PEU2 showed the weight-average molecular weight as 4224 with a polydispersity of 1.06