Shinsaku Shiraishi

Synthesis and properties of novel soluble polyimides having an unsymmetric spiro tricyclic dianhydride unit

A novel spiro trialicyclic dianhydride, rel[1S,5R,6R]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3′-(tetrahydrofuran-2′,5′-dione) (DAn) was synthesized from itaconic anhydride (1) and cyclopentadiene via a Diels-Alder reaction, nitric acid oxidation, and the subsequent dehydration with acetic anhydride. The structure of DAn was determined by NMR spectra and single crystal X-ray diffraction. A series of soluble polyimides (PIs) having a spiro alicyclic unit in the main chain were prepared by the reactions of DAn with several diamines through a general two-step polymerization method. Polymerization temperature affected inherent viscosities of poly(amic acid)s. Chemically imidized PIs had the inherent viscosities in the range of 0.10–0.49 dL/g. Due to the unsymmetric spiro alicyclic structure, the PIs showed excellent solubility in many organic solvents. Glass transition temperatures of PIs ranged from 215 to 279°C and some of them showed no glass transition temperature. The 10% weight loss temperatures under nitrogen were in a range of 355–430°C. Films of PIs obtained by the thermal imidization were wholly transparent and colorless.

A tautomerisable macrocyclic compound containing two aza-bridged 2,2′-bipyridine moieties

A novel macrocyclic compound containing two aza-bridged 2,2′-bipyridine moieties was prepared by the templated reaction of 6,6′-dichloro-2,2′-bipyridine. Spectroscopic investigation shows that the aza-bridging atoms form an amine ⇌; imine tautomeric system. The tautomerism is dependent upon the solvent; the imine form is preferred in non-polar solvents such as chloroform and benzene, while the amine form is favoured almost exclusively in polar solvents such as water, alcohol, acetonitrile, dimethyl sulphoxide, or tetrahydrofuran.

A study on the effect of spirocyclic structures in the main chain on the physical properties of copolyimides

A series of copolyimides were prepared from two alicyclic dianhydrides having the common molecular formula C10H8O6, rel-[1S,5R,6R]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3′-(tetrahydrofuran-2′,5′-dione) (DAn) and c-3-carboxymethyl-r-1,c-2,c-4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride (TCAAH), with p-phenylenediamine (PPD) by a conventional two-step procedure. With increasing DAn fractions in the backbones, the copolyimides showed better film formability, enhanced solubility, increased glass transition temperatures and birefringences, and decreased average refractive indices. The unsymmetric spiroalicyclic structure of DAn might be responsible for these results. Films of copolyimides obtained by both thermal and chemical imidization were fully transparent and were colorless or pale yellow depending on the film thickness.

Dioxygen adducts of cobalt(II) complexes of 6,6′-bis(p-substituted benzoylamino)-2,2′-bipyridines and their catalytic activities in oxygenation of 2,6-di-tert-butylphenol

The oxygen affinities and properties of oxygen adducts of complexes [CoL][H2L = 6,6′-bis(benzoyl-amino)-2,2′-bipyridine and its 4-methyl-, -tert-butyl or -chloro-benzoylamino analogues] has been studied by cyclic voltammetry and IR, electronic and ESR spectroscopy. The complexes exhibited oxygen-binding ability in the presence of an appropriate axial base ligand (B), and the oxygen adducts were of the end-on bonded CoIII(O2–) type [CoL(B)(O2)]. More complete electron transfer from the metal centre to the oxygen was indicated compared to that with [Co(salen)][H2salen =N,N′-ethylenebis(sali-cylideneimine)]. Electron-donating substituents gave higher concentrations of the oxygen adducts. The superior catalytic activity of these complexes, especially the Me- and But-substituted derivatives, in the oxygenation of 2,6-di-tert-butylphenol to the corresponding quinone is interpreted in terms of the reactivity of the co-ordinated oxygen and the oxygen affinity of the complexes.

The extraction and transport of metal ions by 6,6′-diamino-2,2′-bipyridine derivatives

6,6′-Disubstituted-2,2′-bipyridines were studied as to their ability to extract and transport transition- and heavy-metal ions. 6-Amino-6′-dodecyiamino-2,2′-bipyridine (3) has been found to be an excellent synthetic carrier for the specific transport of CuII and CdII ions through a liquid membrane. The effective transport of CdII ion by (3), in spite of its less effective extraction into the organic phase than CuII or ZnII ion, is notable. Moreover, (3) has been shown to have the ability to undergo up-hill transport of both CuII or CdII ions when the proton gradient is available.

Preferential formation of amino acid esters in aqueous alcohol solutions: solvolysis of 6,6′-bis(aminoacylamino)-2,2′-bipyridine by metal coordination

Exclusive formation of amino acid esters took place at an appreciable rate in the CuII-catalysed solvolysis of 6,6′-(α-alanylamino or α-phenylalanylamino)-2,2′-bipyridine in alcohol–borate buffer (pH 7.2) solutions at 20 °C via formation of an amide-O-coordinated complex, even though appreciable amounts of water (0–40% v/v) were present in the solution.

Site selective and quantitative C–N bond cleavage of spermine on a cobalt complex

A C–N bond of spermine coordinated to cobalt(III) is cleaved through site-selective oxidation to yield 1,5-diazabicyclo[4.3.0]nonane and complexes containing 1,3-diaminopropane in an aqueous solution.

Non-template syntheses and monoalkylation of an aza macrocycle containing 2,2′-bipyridine

Cross-condensation of 6,6′-diamino-2,2′-bipyridine (3) with 6,6′-dibromo-2,2′-bipyridine (2) gave an azamacrocycle containing two aza-bridged 2,2′-bipyridine moieties, 3H,10H-tetrapyrido[2,1,6-de:2′,1′,6′-gh:2″,1″,6″-kl:2‴,1‴,6‴-na][1,3,5,8,10,12]hexa-azacyclotetradecine (1), in high yield without metal template. Furthermore, compound (1) could be obtained in >90% yield directly from 6,6′-dibromo-2,2′-bipyridine (2) by heating the latter with ammonia in an autoclave without metal template. N-Alkylation of compound (1) with n-hexyl bromide in the presence of tetra-n-butylammonium bromide gave exclusively the mono-N-n-hexyl derivative of (1), 10-hexyl-3H,10H-tetrapyrido[2,1,6-de:2′,1′,6′-gh:2″,1″,6″-kl:2‴,1‴,6‴-na][1,3,5,8,10,12]hexa-azacyclotetradecine (4). Evidence for the tautomerism of the mono-n-hexyl derivative (4) was provided by the 1H n.m.r. and absorption spectra.

The specific and uphill transport of copper(II) ions by a 6,6′-diamino-2,2′-bipyridine derivative

6-Amino-6′-dodecylamino-2,2′-bipyridine is an excellent synthetic carrier for the specific transport of CuII ions through a liquid membrane, and has the ability to transport CuII ions uphill when a proton gradient is available.

An N2O2 Tetradentate Ligand 6,6′-Bis(Acylamino)-2,2′-Bipyridine. Oxidation-Reduction Properties of Cobalt Complexes

Abstract Recently, we reported the syntheses and the properties of a new type of N2O2 tetradentate ligands, 6,6′-bis(acylamino)-2,2′-bipyridines and their copper(II) complexes. 1. These ligands form two different types of square-planar complexes, i.e., Type 1 and Type 2, depending on the pH of the solution. 1,2 In addition, the deprotonated complexes (Type 2) are suggested to have strong ligand field, and are regarded as analogues of salen complexes. In this paper, we report syntheses and properties of cobalt complexes of 6,6′-bis(benzoylamino)-2,2′-bipyridine (babpH2), and the interaction of the Type 2 complex with molecular oxygen.