Frank E. Smith

The use of microwave ovens for rapid organic synthesis

Abstract Four different types of organic reactions have been studied and seven different organic compounds have been prepared, under pressure in a microwave oven. Considerable rate increases have been observed.

Microwave-assisted sample preparation in analytical chemistry.

The speed and efficiency of instrumentation for chemical analysis has improved dramatically over the past twenty years. Until recently, however, methods of sample preparation had not changed to keep pace, so this had become the slowest step in analytical chemistry methodology. The widespread adoption of domestic microwave ovens during the past twenty-five years has eventually led to their usage in chemical laboratories. Microwave technology has now advanced to the point where it is revolutionizing chemical sample preparation and chemical synthesis. Since the first application of a microwave oven for sample preparation in 1975, many microwave-assisted dissolution methods have been developed - these are applicable to virtually any kind of sample type. This review attempts to summarize all the microwave-assisted dissolution and digestion methods reported up to and including 1994. In addition, some very recent developments in continuous-flow automated dissolution systems are discussed, as is the emergence of databases and software packages related to the application of microwave technology to sample dissolution. There are 344 references.

The preparation, characterization, crystal structure and biological activities of some copper(II) complexes of the 2-benzoylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazate

The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; XCl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(BpSR)X] (BpSR=the benzoylpyridine Schiff bases; RCH3, CH2C6H5; XCl, Br) and [Cu(BpSMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(BpSBz)NO3] complex. The crystal structures of [Cu(BpSMe)NO3] and [Cu(BpSBz)NO3] have been determined by X-ray diffraction studies. The complex [Cu(BpSMe)NO3] crystallizes in the triclinic space group P1 with a=7.600(3), b=10.5346(2), c=11.564(3) A, α=116.0033(14), β=103.91(3), γ=91.55(3)°, V=798.3(4) A and Z=2. The complex has a distorted square-planar geometry with the copper ion lying in an approximate plane of four coordinating atoms, three of which come from the 2-benzoylpyridine Scniff base of S-methyldithiocarbazate while the fourth coordination site is occupied by an oxygen from the nitrate ligand. The complex, [Co(BpSBz)NO3] crystallizes in the monoclinic space group P21/a with a=9.0124(19), b=18.501(5), c=13.0642(24) A, β=106.377(15)°, V=2089(9) A3 and Z=4. The coordination environment around the copper(II) ion is a distorted square-pyramid with three donor atoms (NNS) coming from the 2-benzoylpyridine Schiff base and the fourth and fifth atoms (oxygen) coming from the bidentade NO3− ion. The antifugal and antibacterial properties of the Schiff bases and their copper(II) complexes have been evaluated against three pathogenic fungi and two bacteria. The Schiff bases and copper(II) complexes display moderate antifungal activities but their activities are less than that of the commercially important antifungal agent nystatin.

Possible pre-dissociation of diorganotin dihalide complexes: relationship between antitumour activity and structure.

An examination of crystallographic data has indicated that the structure/activity relationship for diorganotin dihalide complexes is different from that of other metal dihalides, in that the Sn-N bond lengths appear to determine the antitumour activity.

Synthesis and structural studies for a series of aromatic Schiff base complexes with triphenyltin chloride and triphenyltin isothiocyanate

Abstract A series of complexes of formula (C6H5)3SnX·L (X = Cl, NCS) for a range of ligands L, where L = o-HOC6H4CHNC6H4R; o-HOC6H3(OMe)CHNC6- H5 or 2-HOC10H6CHNC6H4R (R = CH3, OCH3) have been synthesised by the reactions of triphenyltin chloride or isothiocyanate with N-aryl-salicylideneimines and N-aryl-2-hydroxynaphthylideneimines. Infrared, PMR, conductivity and Mossbauer data are presented. The crystal structure of one complex, isothiocyanatotriphenyl (1-[(4′-methylphenylimino)- methyl]-2-naphthol)tin(IV), is reported. The crystals are monoclinic, space group P21/c, a = 12.409(1), b = 15.229(3), c = 17.242(2) A, β = 99.828(9)o, V = 3210.5 A3, Z = 4, Dcalc = 1.385 Mg m−3, μ = 0.89 mm−1, F(000) = 1336, T = 295 K, final R = 4.0% for 2898 unique observed reflections. The complex has a five coordinate distorted trigonal bipyramidal structure, with the phenyl groups taking up the equatorial positions around the tin atom. The ligand, which exists in the form of a zwitterion in the complex, binds to the tin via the phenolic oxygen atom. The other complexes are believed to have similar structures to this.

The synthesis, characterization and bioactivities of some copper(II) complexes of the 2-acetylpyridine schiff bases of s-methyl- and s-benzyldithiocarbazate, and the x-ray crystal structure of the nitrato(s-benzyl-β-n-(2-acetylpyridyl) methylenedithiocarbazato)copper(II) complex

Copper(II) complexes of the general formula [Cu(Ap-SMe)X] or [Cu(Ap-SBz)X] (where HAp-SMe and HAp-SBz, respectively, represent the 2-acetylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; XCl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for the [Cu(Ap-SMe)X] (XCl, Br) complexes and a five-coordinate structure for the [Cu(Ap-SBz)NO3] complex. The structure of [Cu(Ap-SBz)NO3] has been determined by X-ray diffraction studies. The geometry of the complex is a distorted square-pyramid with the NNS tridentate ligand and an oxygen atom of the nitrate ion occupying the basal plane. The fifth coordination position is occupied by another oxygen from the nitrate ion. The anti-fungal and anti-bacterial properties of the Schiff bases and their copper(II) complexes have been evaluated against the phytopathogenic fungi A. solanyi, F. equisetti and M. phaseolina and the pathogenic bacteria E. coli and S. aureas. The fungitoxicity of the five-coordinated [Cu(Ap-SBz)NO3] complex approaches that of nystatin, whereas the Schiff base HAp-SMe and its copper(II) complex [Cu(Ap-SMe)NO3] display significant antibacterial activity against E. coli and S. auereas.

The preparation and characterization of some copper(II) Complexes of the 6-methyl-2-formylpyridine thiosemicarbazone and the x-ray crystal structure of the chloro(6-methyl-2-formylpyridinethiosemicabazonato) copper(II) complex

Abstract Copper(II) complexes of general empirical formulae, [Cu(NNS)X] · xH 2 O (NNS = uninegatively charged tridentate ligand formed by condensation of 6-methylpyridine-2-aldehyde with thiosemicarbazide ; X = Cl, Br, NO 3 , and CH 3 COO; x= 0, 1) and [Cu(NNS) 2 ] · 0.5H 2 O have been prepared and characterized by conductance, magnetic, electronic and infrared spectroscopic measurements. Magnetic and spectral data support a square-planar structure for [Cu(NNS)X] (X = Cl, Br, NO 3 , CH 3 COO) and a distorted octahedral structure for [Cu(NNS) 2 ] · 0.5H 2 O. The crystal and molecular structure of [Cu(NSS)Cl] has been determined by X-ray diffraction. This complex has a distorted square-planar geometry with the copper(II) ion lying in an approximate plane of four coordinating atoms, three of which come from the 6-methylpyridine-2-carboxaldehyde thiosemicarbazone and the fourth coordination site is occupied by the chloride ligand. The thiosemicarbazone is present as the thiolate form and is coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the mercaptide sulfur atom. Copyright

The synthesis and structural characterization of some triorganotin(IV) complexes of 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}acetic acid. Crystal and molecular structures of Ph3Sn(2-OHC6H4C(H)NCH2COO) and Me3Sn(2-OHC6H4C(CH3)NCH2COO)

Abstract Triorganotin(IV) derivatives of 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}acetic acid have been synthesized and characterized by 1H, 13C, 119Sn-NMR, 119Sn Mossbauer and IR spectroscopic techniques in combination with elemental analyses. The crystal structures of triphenyltin 2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}acetate and trimethyltin 2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}acetate are reported. The X-ray structures reveal that the complexes adopt a polymeric trans-O2SnC3 trigonal bipyramidal configuration with the R groups in the equatorial positions and the axial locations occupied by a carboxylate oxygen from the ligand and the phenolic oxygen of the ligand on an adjacent complex. The ligands coordinate in the zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. There is hydrogen bonding between this proton and the phenolic oxygen. The carboxylate group is unidentate. The spectroscopic evidence in combination with 119Sn Mossbauer data suggest that the other complexes adopt similar polymeric structures in the solid state.

Synthesis, characterization and fungitoxicities of metal chelates of a pentadentate N3S2 ligand

Abstract The Schiff base obtained by reaction of S-methyldithiocarbazate with 2,6-di-acetylpyridine behaves as a dinegatively charged pentadentate N 3 S 2 chelating agent producing stable crystalline complexes of the general formula, M(SNNNS) (where M = Ni, Cu, Co, Zn and Cd; SNNNS = the dinegative anion of the Schiff base). The complex Fe(SNNNS)C1 was also isolated. Conductivity data and magnetic and spectroscopic evidence support a five-coordinate configuration for the M(SNNNS) complexes and an octahedral configuration for the Fe(SNNNS)Cl complex. Fungitoxicities of the Schiff base and its metal complexes against three plant pathogens viz. Alternaria solani, Curvularia geniculata and Colletotrichum capsici have been studied. The ligand and its complexes display marked antifungal activities against all the test fungi.

Six-coordinate tin in a dialkylchlorooxinatotin(IV) complex: skew-trapezoidal bipyramidal bis(2-carbomethoxyethyl)chloro(quinolin-8-olato)tin(IV)

Bis(2-carbomethoxyethyl)chloro(quinolin-8-olato)tin(IV), C17H20ClNO5Sn, crystallizes in the triclinic space group P1, with a 7.9001(7), b 10.2636(7), c 12.8287(9) A; α 108.575(7), β 98.564(6), γ 96.469(7)°; V 960.69 A3, Z = 2. The coordination geometry around the tin atom approximates to a skew-trapezoidal bipyramid, with the carbonyl oxygen of one of the 2-carbomethoxyethyl groups intramolecularly bonded to the tin (SnO 2.847(4) A). This oxygen atom, the nitrogen and oxygen atoms of the chelating quinolin-8-olato ligand (SnN 2.370(4), SnO 2.040(4) A; NSnO 74.4(1)°), and the chlorine atom (SnCl 2.454(2) A), occupy the four corners of a trapezoid around the metal atom. The two apical tincarbon bonds (SnC 2.122(6), 2.143(7) A), which are skewed towards the long edge (defined by the carbonyl oxygen and nitrogen atoms) of the trapezoidal plane, subtend an angle of 135.4(3)° at tin.