Tim Higgins

Isolation and characterization of a thermostable endo-β-glucanase active on 1,3-1,4-β-D-glucans from the aerobic fungus Talaromyces emersonii CBS 814.70

Abstract A novel endoglucanase active on 1,3-1,4-β- d -glucans was purified to apparent homogeneity from submerged cultures of the moderately thermophilic aerobic fungus Talaromyces emersonii CBS 814.70. The enzyme is a single subunit glycoprotein with Mr and pI values of 40.7 ± 0.3 kDa and 4.4, respectively, and an estimated carbohydrate content of 77% (w/w). The purified β-glucanase displayed activity over broad ranges of pH and temperature, yielding respective optima values of pH 4.8 and 80°C. This enzyme was markedly thermostable with 15% of the original activity remaining after incubation for 15 min at 100°C. Substrate specificity studies revealed the identity of the enzyme to be a 1,3-1,4-β- d -glucanase. Identical Km values (13.38 mg.ml−1) were obtained with lichenan and BBG, while the Vmax value with lichenan (142.9 IU.mg−1) was approximately twice the value obtained with BBG (79.3 IU.mg−1). Time-course hydrolysis of barley-β-glucan did not proceed linearly with respect to time indicating an ‘endo’ or more processive action for the enzyme. HPAEC fractionation of the products of hydrolysis yielded a range of oligosaccharides, with cellobiose, cellotriose and cellotetraose being the predominant oligosaccharide products.

Transition-metal Schiff-base complexes as ligands in tin chemistry. Part 7. Reactions of organotin(IV) Lewis acids with [M(L)]2 [M=Ni, Cu and Zn; H2L=N,N′-bis(3-methoxysalicylidene)benzene-1,3-diamine and its -1,4-diamine analog]

Dinuclear complexes [M(3MeO-sal- m -phen)(H 2 O)] 2 [M=Cu, Ni and Zn; 3MeO–H 2 sal- m -phen= N,N ′-bis(3-methoxysalicylidene)benzene-1,3-diamine] and [M(3MeO-sal- p -phen)(H 2 O)] 2 [M=Cu, Ni and Zn; 3MeO–H 2 sal- p -phen= N,N ′-bis(3-methoxysalicylidene)benzene-1,4-diamine] were synthesised and reacted with diorganotin(IV) dihalides, dinitrates and dithiocyanates. Only in the case of those reactions involving [M(3MeO-sal- m -phen)(H 2 O)] 2 with M=Ni or Zn were adducts obtained as the sole products of reaction; the adducts were all tetranuclear complexes. The tetranuclear adduct {(SnBu n 2 ).[Ni(3MeO-sal- m -phen)(NCS) 2 ]} 2 · 6MeCN results from salicylaldimine ligands, related by a 2-fold axis, adopting bridging roles by co-ordinating to each of the symmetry related nickel atoms through phenolic oxygen and imine nitrogen atoms, while their phenolic and methoxy oxygen atoms form donor bonds to the tin atoms of symmetry related dibutyltin cations. The salicylaldimine ligands, related by inversion, adopt the same bridging role towards the nickel atoms in the adduct {[SnBz 2 (NO 3 )]·[Ni(3MeO-sal- m -phen)(NO 3 )]} 2 .6MeCN (Bz=benzyl), but as a result of the bidentate role of the nitrate co-ordinated to nickel, the arrangement of the phenolic and methoxy oxygens is such that each tin is co-ordinated quite strongly by a bidentate nitrate, a methoxy and two phenolic oxygen atoms while a second methoxy oxygen provides a weak Sn–O interaction, thus resulting in pseudo eight co-ordinate tin. 119 Sn Mossbauer parameters indicate that all of the adducts of di- and triorganotin halides are organotin aqua adducts with the donor water engaged in hydrogen bonding with Schiff-base oxygen atoms.

Transition metal Schiff-base complexes as ligands in tin chemistry: IV. Reactions of triphenyltin chloride with divalent metal salicylaldimine complexes and the molecular structures of [SnPh3Cl · H2O][Ni(3-MeOsal1,3pn) · H2O] (1:1) and [SnPh3Cl · H2O]Ni(3-MeOsal1,3pren) (1:1) [H23-MeOsal1,3pn N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine]

Abstract Unlike diorganotin(IV) dihalides, triphenyl- and tribenzyl-tin chlorides do not react with Schiff-base complexes M(SB) (M  Cu II , Ni II and Zn II ; SB  N , N ′-ethylenebis-salicylideneaminato and related salicylaldimine ligands). Triphenyltin chloride does however form 1:1 addition complexes with 3,3′-methoxy substituted salicylaldimines of Ni II and Cu II , but only in the presence of water. Each of these complexes contains the aquo adduct SnPh 3 Cl · H 2 O, with the donor water molecule engaged in hydrogen bonding interactions with the four oxygen atoms of the divalent metal salicyaldimine. These structural features were confirmed crystallographically for (SnPh 3 Cl · H 2 O)Ni(3-MeOsal1,3pn) (1:1) [H 2 3-MeOsal1,3pn  N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine]. In the case of [SnPh 3 Cl · H 2 O][Ni(3-MeOsal1,3pn) · H 2 O] (1:1) both the water molecule coordinated to nickel and the water molecule coordinated to tin engage in hydrogen bonding interactions with the Schiff-base oxygen atoms, thereby creating centrosymmetric hydrogen-bonded dimers.

Transition-metal Schiff-base complexes as ligands in tin chemistry. Part 3. An X-ray crystallographic and tin-119 Mössbauer spectroscopic study of adduct formation between tin(IV) Lewis acids and nickel 3-methoxysalicylaldimine complexes

1:1 Addition complexes of [NiIIL]·H2O [H2L =N,N′-bis(3-methoxysalicylidene)ethylenediamine (3MeO-H2salen), N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine (3MeO-H2salpn) or N,N′-bis(3-methoxysalicylidene)-o-phenylenediamine (3O-H2salphen)] with SnR2Cl2(R = Me or Ph), SnBunCl3, or SnCl4 have been found to be generally monoaqua adducts of the tin Lewis acids with the water engaged in hydrogen bonding with the methoxy and phenolic oxygen atoms of the Schiffbase ligand. Both water and methoxy oxygen atoms are involved in donor-bond formation to tin in the polymeric structures 2SnMe2Cl2·[Ni(3MeO-salen)]·H2O and SnMe2Cl2·[Ni(3MeO-salphen)]·H2O, each of which has two very different tin environments. The two octahedral tin sites in the structure of SnMe2Cl2·2[Ni(3MeO-salphen)·H2O] appear to result from two isomeric forms of the adduct co-existing in a lattice as a result of hydrogen-bonding interactions. Crystal-structure determinations revealed that the monoaqua adducts of dimethyltin dichloride which exist in the structures SnMe2Cl2·[Ni(3MeO-salen)]·H2O and SnMe2Cl2·[Ni(3MeO-salon)]·H2O differ in that, in the former tin is in a trigonal-bipyramidal environment, whereas in the latter it is in an octahedral environment as a result of an intermolecular Sn ⋯ Cl contact of 3.615 A.

Synthesis and antispasmodic activity of nature identical substituted indanes and analogues

Abstract The synthesis of a series of substituted indanes which provide routes to nature-identical compounds and their analogues is reported. The smooth muscle relaxant activity of a series of substituted indanes and indanones together with their analogues has been measured. A compound with significant smooth muscle relaxant activity has been identified.

Transition-metal Schiff-base complexes as ligands in tin chemistry Part 6. Reactions of diorganotin(IV) dinitrates with M(3MeO-sal1,3pn) [M = Ni, Co or Zn; H23MeO-sal1,3pn = N,N′-bis(3-methoxysalicylidene)-propane-1,3-diamine]

Abstract Reactions of diorganotin(IV) dinitrates with M(3MeO-sal1,3pn) · H 2 O (M = Ni, Co or Zn; H 2 3MeO-sal1,3pn = N , N ′-bis(3-methoxysalicylidene)propane-1,3-diamine) leads to nitrate migration from tin to the transition metal or zinc and the formation of intimate ion-paired bimetallic 1 1 addition complexes. In each of these complexes the tin atom is located in the plane of the Schiff-base oxygens and is coordinated by all four. The complexes [SnBz 2 (NO 3 )] · [M(3MeO-sal1,3pn)(NO 3 )](M = Co or Zn) are isomorphous and each contains tin in a pentagonal bipyramidal environment with the four Schiff-base oxygens and a nitrate oxygen defining the equatorial plane. In the case of {[SnMe 2 ] · [Ni(3MeO-sal1,3pn)(NO 3 )(H 2 O)]}NO 3 , the tin is six-coordinated, but there is an additional weak intermolecular SnO interaction involving an oxygen of a nitrate coordinated to nickel. The complex {[SnMe 2 (H 2 O)] · [Co(3MeO-sal1,3pn)(NO 3 )(H 2 O)]}NO 3 contains tin in a pentagonal bipyramidal environment with the Schiff-base oxygens and a water oxygen defining the equatorial plane. The crystal structures of both dimethyltin complexes display extensive hydrogen bonding.

Transition-metal Schiff-base complexes as ligands in tin chemistry. Part 5. Structural studies of intimate ion-paired heterobimetallic complexes of tin(IV) and nickel, copper or zinc with 3-methoxysalicylaldimine ligands

1 : 1 Adducts have been formed between SnMe2(NCS)2 and SnBun2(NCS)2 with [Ni(3MeO-salpd)]·H2O [3MeO-H2salpd =N,N′-bis(3-methoxysalicylidene)propane-1.3-diamine] and [Ni(3MeO-salbn)]·H2O [3MeO-H2salbn =N,N′-bis(3-methoxysalicylidene)butane-1,4-diamine] and are best represented as the intimate ion-paired adducts [SnR2]2+·[NiL(NCS)2]2–[L = Schiff-base ligand; R = Me or Bun] in each of which the tin atom sits in the plane of, and is held by donor bonds from, the four Schiff-base oxygen atoms. A crystal-structure determination of [SnMe2]2+·[Ni(3MeO-salpd)(NCS)2]2– revealed a tin co-ordination geometry which can be described as skew trapezoidal bipyramidal. The large unoccupied volume of the tin co-ordination sphere results in tin readily increasing its co-ordination number to seven, as demonstrated crystallographically in [SnMe2·dmf]2+·[Ni(3MeO-salpd)(NCS)2]2+(dmf = dimethyl-formamide), which contains tin in a pentagonal-bipyramidal co-ordination environment with trans methyl groups and five donor oxygen atoms in the equatorial plane. X-Ray structural studies of both [SnBun2]2+·[Ni(3MeO-salpd)(NCS)2]2– and [SnBun2]2+·[Ni(3MeO-salbn)(NCS)2]2– revealed the presence of molecular association resulting from weak intermolecular thiocyanate contacts, thus providing each tin with pseudo-pentagonal-bipyramidal co-ordination geometry. These latter adducts readily formed tin donor bonds with dmf. The 1:1 adduct formed between SnPh2(NCS)2 and [Ni(3MeO-salpd)]·H2O was shown, from an X-ray crystallographic study, to be the intimate ion-paired heterobimetallic complex [SnPh2(NCS)]+·[Ni(3MeO-salpd)(NCS)(MeCN)]– in which tin has pentagonal-bipyramidal geometry with trans phenyl groups. Infrared and tin-119 Mossbauer spectroscopic data clearly demonstrate that a similar pentagonal-bipyramidal co-ordination geometry exists about tin in the complexes [SnR2(NCS)]+·[ML(NCS)]–·nH2O (R = Me or Bun; M = Cu or Zn; n= 0, 1 or 2).

Molecular materials containig donor and acceptor groups. Synthesis, structure and spectroscopic properties of ferrocenyl Schiff bases

Ferrocenyl Schiff-base derivatives of the form [Fe(η-C5H5)(η-C5H4CHNR)][R = NCH(C6H4NO2-p)1, C6H4CN-p2, C6H4NO2-p3, C6H4F-p4, C6H4Cl-p5, C6H4Br-p6, C6H4NO2-m7, NH(C6H4NO2-o)8, NH(C6H4NO2-p)9 or NH(C6F5)10], have been prepared from ferrocenecarbaldehyde. Proton, 13C NMR, UV/VIS and 57Fe Mossbauer spectroscopic data are presented. A number of these derivatives contain the donor–π-acceptor-(D–π-A) structural motif desired for non-linear optical materials. The behaviour of the ferrocenyl moiety as a donor is compared to that of the 4-dimethylaminophenyl group. The UV/VIS spectra of compound 1 showed considerable solvatochromism. As a result of this and its extended donor–π-acceptor nature, 1 was tested for non-linear optical properties, specifically, second harmonic generation. The results, however, were negative. A single-crystal X-ray study revealed 1 to crystallize in a centrosymmetric space group P21/n, with a= 5.885(1), b= 30.745(3), c= 8.662(1)A, β= 96.40(2)° and Z= 4. The most striking feature of the molecular structure is the coplanarity of the substituent group with the η-C5H4 ring of the ferrocenyl moiety. The crystal structure reveals stacks of ferrocenyl, phenyl, phenyl, ferrocenyl moieties with inter-ring distances of 3.529 A between the C5–C6 rings and 3.478 A between the C6–C6 ring planes. The observation of a DAAD in contrast to a DADA stack is discussed.

The 2,3-epoxide, a donor in lanthanide shift-reagent studies of carbohydrate systems; the x-ray structure of methyl 2,3-anhydro-4,6-O-benzylidene-β-d-mannopyranoside

Abstract Lanthanide-induced shifts in the 1 H-n.m.r. spectra of the methyl 2,3-anhydro-4,6- O -benzylidene- d -hexopyranosides [ manno ( 1 and 5 ), allo ( 2 and 6 ), gulo ( 3 and 7 , α and β, respectively, and α- talo ( 4 )] have been measured. The observed shift data for the α- manno , β- allo , and β- gulo epoxides were in good agreement with those calculated for the ° H 5 conformation of the pyranoid ring using a single-site model. Shifts calculated for the ° H 5 conformation of the β- manno epoxide using a two-site model were in excellent agreement with the observed shift data. The 13 C-n.m.r. spectra were assigned by decoupling techniques, and n.m.r. line-shifts ( 1 H and 13 C) induced by the shift reagents were used in some cases for complete assignment of signals. The solid-state structure of methyl 2,3-anhydro-4,6- O -benzylidene-β- d -mannopyranoside ( 5 ) has been determined by X-ray crystallographic analysis.

Oxidative activation of CoII in Schiff base complexes in the presence of n-butyltin trichloride: the molecular structure of BunSn(OMe)Cl2·CoCl(salen)[salen =N,N′-ethylenebis(salicylideneaminato)]

Air stable chloroform solutions of Schiff base complexes of CoII undergo rapid cobalt oxidation on addition of n-butyltin trichloride yielding complexes in which, as exemplified by the crystal structure of BunSn(OMe)Cl2·CoCl-(salen)[salen =N,N′-ethylenebis(salicylideneaminato)], the cobalt(III) Schiff base species behave as Lewis bases towards tin(IV).