Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Sau-Fun Tan is active.

Publication


Featured researches published by Sau-Fun Tan.


Transition Metal Chemistry | 1984

Synthesis and characterisation of copper(II), nickel(II) and palladium(II) complexes of some schiff bases of dehydroacetic acid

Sau-Fun Tan; Kok-Peng Ang; Hari Lakshmi Jayachandran

SummaryTri-and quadri-dentate Schiff bases have been synthesized from the reaction of dehydroacetic acid with diamines, aminoacids, aminophenols and aminoalcohols. The copper(II) and some nickel(II) and palladium(II) chelates of these ligands as well as copper(II) complexes of bidentate Schiff bases of dehydroacetic acid with anilines have been prepared and characterised by electronic, i.r. and n.m.r. spectral measurements and magnetic moments.


Transition Metal Chemistry | 1988

Unsymmetrical bis-Schiff bases derived from ethylenediamine, dehydroacetic acid and another aldehyde/ketone and the preparation and characterisation of their copper(II) and nickel(II) complexes

Sau-Fun Tan; Kok-Peng Ang

SummaryPartial displacement of the symmetrical bis-Schiff bases (1)–(4) of ethylenediamine and salicyladehyde, o-hydroxyacetophenone, acetylacetone or benzoylacetone by dehydroacetic acid have led to the formation and isolation of the unsymmetrical bis-Schiff base ligands (6)–(9). Attempted partial displacements of the symmetrical bis-Schiff base (5) of dehydroacetic acid or (1)–(4) by each of the other four carbonyl compounds have been unsuccessful. The Ni(II) and Cu(II) complexes of (6)–(9) have been prepared and characterized.


Journal of The Chemical Society-perkin Transactions 1 | 1986

(Z)- and (E)-5-Arylmethylenehydantoins: spectroscopic properties and configuration assignment

Sau-Fun Tan; Kok-Peng Ang; Yoke-Fan Fong

Both (Z)- and (E)-5-arylmethylene-1-methylhydantoins have been obtained directly in substantial proportions from condensations of 1-methylhydantoin with aromatic aldehydes. However, the products of similar condensations of hydantoin or 3-methylhydantoins consist almost entirely of the Z-isomers. The configurations of all the 5-arylmethylenehydantoins prepared can be unambiguously assigned by consideration of their 1H and 13C n.m.r., i.r., and u.v. spectra. The mass spectra of the isomers show similar fragmentation patterns.


Transition Metal Chemistry | 1990

Oxygenation of the cobalt(II) complex of an unsymmetrical bis-Schiff base

Sau-Fun Tan; Kok-Peng Ang; Lai-Har Ng; Alwyn G. Davies; Dan Oprescu

SummaryThe cobalt(II) complex of an unsymmetrical bis-Schiff base. Co(dha, salen), has been prepared. In the presence of pyridine, it forms both monomeric superoxo and dimeric peroxo adducts with dioxygen. At −10°C and lower temperatures, the adduct formed in pyridine solution is mainly superoxo as shown by electronic and e.s.r. spectra as well as volumetric measurement of oxygen uptake. The solid adduct precipitated by addition of toluene is predominantly peroxo as shown by elemental analysis, i.r. spectrum, magnetic and thermogravimetric measurements. Comparison of the oxygen affinities of this complex and of the symmetrical Co(salen) is discussed.


Transition Metal Chemistry | 1991

Catalytic autooxidation ofp-anisaldehyde and styrene by a cobaltbis-schiff base complex

Sau-Fun Tan; Pak-Hing Leung; Wun-Chey Sin

SummaryThe CoII complex derived from the unsymmetricalbis-Schiff base ligand, 3-[1-[[2-[[(2-hydroxyphenyl)methylene]-amino]ethyl]amino]ethylidene]-6-methyl-2H-pyran-2,4(3H) dione H2(dha, salen), is a catalyst for the autoxidation of aromatic aldehydes. Under ambient condition Co(dha, salen) catalyses the oxidation ofp-anisaldehyde top-anisic acid in quantitative yield (250 turnovers). The presence of Co(dha, salen) also accelerates the co-oxidation ofp-anisaldehyde and styrene (88 turnovers). In the co-oxidation process, styrene is selectively converted to styrene oxide as the major product.


Journal of The Chemical Society-perkin Transactions 1 | 1988

Ionization constants of 5-arylmethylenehydantoins in 80%(w/w) dimethyl sulphoxide–water at 25 °C

Sau-Fun Tan; Kok-Peng Ang; Yoke-Fan Fong; Harilakshmi Jayachandran

The pK values of (Z)-5-arylmethylenehydrantoins, (Z)-5-arylmethylene-3-methylhydantoins, and (Z)- and (E)-5-arylmethylene-1-methylhydantoins with various para-substituents in the phenyl ring have been measured. The effects of structure and stereochemistry on acidity are discussed. For each series, a good linear correlation is obtained between the pK values and Hammett constants σ and σ– in spite of the considerable distance of the site of deprotonation from the phenyl ring. The ρ values show that substituent effects are significantly greater on the acidity of N(1)–H than on that of N(3)–H, and are also greater for the E- than the Z-isomers of the 5-arylmethylene-1-methylhydantoins.


Journal of The Chemical Society-perkin Transactions 1 | 1983

Ionization constants of some Schiff's bases in 80%(w/w) dimethyl sulphoxide–water solvent at 25 °C

Sau-Fun Tan; Kok-Peng Ang; Harilakshmi Jayachandran

pK Determination in 80%(w/w) dimethyl sulphoxide–water solvent at 25 °C has been used as a means of studying the tautomerism in a series of Schiffs bases derived from some C-acylhydroxypyrones. While their much lower acidities compared with the corresponding parent compounds indicate a predominance of ketoamine tautomers, their higher acidities compared with amides and other nitrogen acids suggest significant contributions from dipolar structures. Correlation of the wide range of pK values with the structures is discussed.


Journal of The Chemical Society-perkin Transactions 1 | 1983

Ionization constants of some hydroxypyrones in water and in 80%(w/w) dimethyl sulphoxide–water at 25 °C

Sau-Fun Tan; Kok-Peng Ang; Harilakshmi Jayachandran

The ionization constants of some hydroxypyrones have been measured spectrophotometrically at 25 °C in water and in 80%(w/w) dimethyl sulphoxide–water. A few of them are exceptionally strongly acidic. The pKa values of these compounds are discussed in relation to their molecular structures. A plot of the pKa in water against the corresponding pKa in 80%(w/w) dimethyl sulphoxide–water is linear, although ΔpKa varies from negative values for the weaker acids to positive values for the stronger acids. Possible solvent effects have been suggested.


Journal of The Chemical Society-perkin Transactions 1 | 1988

Thermal equilibration of Z- and E-isomers of 5-arylmethylenehydantoins. Evidence for non-bonded aromatic π⋯ methyl attractions

Sau-Fun Tan; Kok-Peng Ang; Gee-Fung How

Standard free energy differences between the Z- and E-isomers of 14 5-arylmethylenehydantoins have been estimated by thermal equilibration in dimethyl sulphoxide. The Z-configuration is more stable for the N-unsubstituted compounds while the E-configuration is preferred for those N-1methyl derivatives with only para-substituents in the aryl group. The ΔG° values vary with the nature of the para-substituents. For those N-1 methyl derivatives with two ortho-substituents in the aryl group, the configurational preference is dependent on the electronic effects of these aryl substituents, suggesting the presence of non-bonded aromatic π⋯ Me interactions. The factors influencing the relative stabilities of Z- and E-isomers are discussed.


Journal of The Chemical Society-perkin Transactions 1 | 1979

Ionization constants of some hydroxy-pyrones at 25 °C

Kok-Peng Ang; Sau-Fun Tan

The ionization constants of some hydroxy-pyrones have been measured in aqueous solutions by a spectrophotometric method and compared with those of analogous phenols. The strikingly high acidity of 3,5-diacetyl-4,6-dihydroxy-2-pyrone has been explained by the formation of a symmetrical and extensively resonance-stabilized monoanion through ionization of the C-6 hydroxy-group.

Collaboration


Dive into the Sau-Fun Tan's collaboration.

Top Co-Authors

Avatar

Kok-Peng Ang

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

Harilakshmi Jayachandran

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

Gee-Fung How

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

W.L. Kwik

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

Peter T.-H. Wong

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

Phee-Teik Yeoh

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Alan J. Jones

Australian National University

View shared research outputs
Top Co-Authors

Avatar

Hari Lakshmi Jayachandran

National University of Singapore

View shared research outputs
Top Co-Authors

Avatar

How Sung Lee

National University of Singapore

View shared research outputs
Researchain Logo
Decentralizing Knowledge