Electrostatic Assembly of Dendrimer Electrolytes: Negatively and Positively Charged Dendrimer Porphyrins

Carboxylate and ammonium functionalities—32 of each— facilitate electrostatic interaction between oppositely charged dendrimer electrolytes and porphyrin cores, which leads in protic media to a supramolecular, fluorescence-active aggregate of two chromophores that communicate and have a predictable topology (see drawing on the right; A=acceptor, D=donor). In contrast to the complexation of linear polyelectrolytes, the contact area for the two dendrimer molecules is very limited, just as one would expect for an assembly of spherical molecules.     

Functionalization and Dispersion of Hexagonal Boron Nitride (h‐BN) Nanosheets Treated with Inorganic Reagents

A mixture of bulk hexagonal boron nitride (h‐BN) with hydrazine, 30 % H₂O₂, HNO₃/H₂SO₄, or oleum was heated in an autoclave at 100 °C to produce functionalized h‐BN. The product formed stable colloid solutions in water (0.26–0.32 g L ^?1) and N,N‐dimethylformamide (0.34–0.52 g L ^?1) upon mild ultrasonication. The yield of “soluble” h‐BN reached about 70 wt %. The dispersions contained few‐layered h‐BN nanosheets with lateral dimensions in the order of several hundred nanometers. The functionalized dispersible h‐BN was characterized by IR spectroscopy, X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV/Vis spectroscopy, X‐ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). It is shown that h‐BN preserves its hexagonal structure throughout the functionalization procedure. Its exfoliation into thin platelets upon contact with solvents is probably owing to the attachment of hydrophilic functionalities.     

Toward Ultralow‐Bandgap Liquid Crystalline Semiconductors: Use of Triply Fused Metalloporphyrin Trimer–Pentamer as Extra‐large π‐Extended Mesogenic Motifs

In contrast with their dimeric homologue, triply fused zinc porphyrin trimer–pentamer, as extra‐large π‐extended mesogens, assemble into columnar liquid crystals (LCs) when combined with 3,4,5‐tri(dodecyloxy)phenyl side groups ( 3 P_Zn – 5 P_Zn , Figure 1 ). Their LC mesophases develop over a wide temperature range, namely, 41–280 °C (on heating) for 5 P_Zn , and all adopt an oblique columnar geometry, typically seen in columnar LC materials involving strong mesogenic interactions. These LC materials are characterized by their wide light‐absorption windows from the entire visible region up to a near infrared (NIR) region. Such ultralow‐bandgap LC materials are chemically stable and serve as hole transporters, in which 5 P_Zn gives the largest charge carrier mobility (2.4×10^?2 cm V^?1 s^?1) among the series. Despite a big dimensional difference, they coassemble without phase separation, in which the resultant LC materials display essentially no deterioration of the intrinsic conducting properties.     

Cation transport by a redox-active synthetic ion channel

The synthesis, cation binding and transmembrane conductive properties of a novel group of synthetic ion channels containing a redox-active centre are described. Experiments using a black lipid membrane preparation revealed that these compounds function effectively as ion channels. Subsequent 23Na NMR spectroscopy studies focused on a synthesized ion channel with a ferrocene centre. When incorporated in vesicular bilayers, this channel was demonstrated to support a Na+ flux that was at least six times faster than ion transport by monensin. Since oxidation of the ferrocene moiety completely inhibited the Na+ transport, the redox-active centre provides a potential mechanism for controlling ion flux.     

Characteristics of organic transformations in a confined dendritic core: studies on the AIBN-initiated reaction of dendrimer cobalt(II) porphyrins with alkynes

Cobalt(II) complexes of poly(aryl ester) dendrimer porphyrins [(m-[Gn]TPP)Co(II)] (generation number n=0-4), in the presence of azobisisobutyronitrile (AIBN) at 60 degrees C, underwent alkenylation with several alkynes at the metal center. A complete inhibition of double-bond migration (secondary transformation) was observed for [(m-[Gn]TPP)Co(II)] (n=3 and 4), which gave [(m-[Gn]TPP)Co(III)-C(=CH(2))R] (n=3 and 4) exclusively. Overall reaction rates for [(m-[Gn]TPP)Co(II)] (n=0-3) were hardly dependent on the size of the dendritic substituents, while a notable retardation was observed for the largest dendrimer, [(m-[G4]TPP)Co(II)]. Mechanistic studies on double-bond migration with pure [(m-[Gn]TPP)Co(III)-C(=CH(2))Bu] (n=0-4) demonstrated that the secondary transformation involves participation of [(m-[Gn]TPP)Co(III)H] (n=0-4), derived from [(m-[Gn]TPP)Co(II)] and AIBN, rather than [(m-[Gn]TPP)Co(II)] alone. Crossover experiments using [(m-[Gn]TPP)Co(III)-C(=CH(2))Bu] (n=2-4), in combination with nondendritic [(m-[G0]TPP)Co(II)] and AIBN, indicated a high level of steric protection of the active center by a robust [G4]-dendritic cage, as suggested by a (1)H NMR pulse relaxation time profile of m-[G4]TPPH(2).     

Nonlinear amplification of circular dichroism activity upon cyclodimerization of a chiral saddle-shaped porphyrin

A cyclic dimer of chiral saddle-shaped porphyrin with p-xylylene linkers, upon interaction with mandelic acid, showed an enhanced circular dichroism activity, which was more than 7 times as large as that of a monomeric reference.     

Solvent-Free Synthesis of Nano Zirconium Phenylphosphonates with Molten Phenylphosphonic Acid

Nanosized α-zirconium phenylphosphonate particles were successfully prepared by the reaction between different zirconium sources and molten phenylphosphonic acid in the absence of solvent. The resultant nanoplates exhibit particle sizes in the range of 15 to 30 nm. The use of a topotactic anion exchange method starting from α-zirconium phosphate instead resulted in the generation of 15 to 180 nm plates, while also resulting in nanoparticles with a higher degree of crystallinity. The topotactic anion exchange of the phosphate groups by phenylphosphonate groups could be performed to completion when performed in molten phenylphosphonic acid. Characterization of both the final products as well as the individual steps in the anion exchange were performed by powder XRD, fast neutron activation analysis, TGA, FTIR spectroscopy, TEM, solid-state NMR and XPS.     

NMR Studies on Solution Structures of Methanol and Ethanol Saturated with CO2

²H and ¹⁷O NMR relaxation times, T ₁(²H) and T ₁(¹⁷O), and ²H NMR chemical shifts, δ(²H), in CO₂-saturated CD₃OD and C₂D₅OD solutions were measured at 313.2 K over the pressure range up to ~6 MPa. The rotational correlation times, τ _r, of the CD and OD axes within CD₃OD and C₂D₅OD molecules and the CO axis within the CO₂ molecule were determined from T ₁(²H) and T ₁(¹⁷O), and the magnetic susceptibility-corrected chemical shifts, δ _corr, were derived from δ(²H). The differences in τ _r and δ _corr observed between the two alcohol systems: τ _r and δ _corr of OD in C₂D₅OD, decreased rapidly with increasing CO₂ concentration, while those of OD in CD₃OD remained almost unchanged at mole fractions of CO₂, \( x_{\text CO_{2}} \) , lower than ~0.25 and then slightly decreased at higher \( x_{\text CO_{2}} \) . The hydrogen bonding structure in C₂D₅OD was found to be gradually broken down by CO₂ dissolution. On the other hand, in CD₃OD, it has been revealed that the hydrogen bonding structure can persist at \( x_{\text CO_{2}} \)  < ~0.25 but then collapses at higher \( x_{\text CO_{2}} \) .     

Microwave irradiation： Novel and facile methods for the synthesis of new pyrimidinones

We describe here a rapid process for the preparation of new 9-chloromethyl-12-aryl-10,12-dihydrobenzo[5,6]chromeno[2,3-d]pyrimidin-11-ones 5a-d and 10-chloromethyl-7-aryl-7,9-dihydrobenzo[7,8]chromeno[2,3-d]pyrimidin-8-ones 6a-d by two different methods utilizing microwave irradiation. This methodology provides better yields(72%–80%) and high purity of the title compounds.     

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

The Schiff bases of N(2)O(2) dibasic ligands, H(2)La and H(2)Lb are prepared by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. Also tetra basic ligands, H(4)La and H(4)Lb are prepared by the condensation of aliphatic amines (a) and (b) with 6-formyl-5,7-dihydroxy-2-methylbenzopyran-4-one. New complexes of H(4)La and H(4)Lb with metal ions Mn(II), Ni(II) and Cu(II) are synthesized, in addition Mn(II) complexes with ligands H(2)La and H(2)Lb are also synthesized. Elemental and thermal analyses, infrared, ultraviolet-visible as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The structures of copper(II) complexes are also assigned based upon ESR spectra study. All the complexes separated with the stoichiometric ratio (1:1) (M:L) except Mn-H(4)La and Mn-H(4)Lb with (2:1) (M:L) molar ratio. In metal chelates of the type 1:1 (M:L), the Schiff bases behave as a dinegative N(2)O(2) tetradentate ligands. Moreover in 2:1 (M:L) complexes, the Schiff base molecules act as mono negative bidentate ligand and binuclear complex is then formed. The Schiff bases were assayed by the disc diffusion method for antibacterial activity against Staphylococcus aureus and Escherichia coli. The antifungal activity of the Schiff bases was also evaluated against the fungi Aspergillus flavus and Candida albicans.