Norman M. Macdonald

Synthesis and co-ordination chemistry of the sterically demanding pendant-arm macrocycle N,N′,N″-tris[(2R)-2-hydroxy-3-methylbutyl]-1,4,7-triazacyclononane

The sterically demanding pendant-arm macrocycle N,N′,N″-tris[(2R)-2-hydroxy-3-methylbutyl]-1,4,7-triazacyclononane H3L has been synthesised. Owing to its bulky isopropyl arms the formation of dimeric species is prevented which is in contrast to the behaviour of the analogous ligand with methyl substituted arms, N,N′,N″-tris[(2R)-2-hydroxypropyl]-1,4,7-triazacyclononane (H3L′). The preparation of complexes of VIV,CrIII, MnIV NiII, CuII and ZnII with H3L is described and the crystal structures and some spectroscopic properties of [MnIVL][PF6]·H2O and [NiII(H3L)][NO3][PF6] determined.

Synthesis, x-ray crystal structure and spectroscopy of the hydrogen-bridged dimer [CrIII(L · H3L)CrIII][PF6]3 (H3L = N,N′,N″-tris[(2S)-2-hydroxypropyl]-1,4,7-triazacyclononane)

Abstract The preparation, structure and spectroscopy of [Cr III (L · H 3 L)Cr III ][PF 6 ] 3 (H 3 L = N , N′ , N″ -tris[(2 S )-2-hydroxypropyl]-1,4,7-triazacyclononane) are presented. The complex is a hydrogen-bridged dimer with three symmetric O-H-O bridges. The coordination round the Cr I is is preudo-octahedral with a twist away from octahedral geometry of 15°. The dimer is broken up under both acid and basic conditions to give [Cr III LH 3 ] + and [Cr III L], respectively. The CD spectra of the three species are interpreted as showing that there is a smaller twist away from octahedral geometry in the monomers than in the dimer. The preparation of [Cr III ( S -mtcta = N , N′ , N″ -trisacetato-(2 S )-2-methyl-1, 4,7-triazacyclononane) is also reported and its spectra compared with those of [Cr III (L·H 3 L)Cr III ] 3+ .

Synthesis and crystal structure of [MnII(H3L)(L)MnIV][PF6]3[H3L =N,N′,N″-tris-(2S)-2-hydroxypropyl-1,4,7-triazacyclononane]: a mixed-valence pendant-arm macrocycle dimer in which the ligand adopts different angular geometries at the two metal centres

Reaction of N,N′,N″-tris-(2S)-2-hydroxypropyl-1,4,7-triazacyclononane (H3L) with MnCl2 in neutral or slightly basic conditions affords (MnII(H3L)(L)MnIV][PF6]3, a mixed-valence, hydrogen-bridged dimer in which the MnIV half has pseudooctahedral geometry and the MnII half has trigonal prismatic geometry.

Logistic Growth of a Single Species

To obtain a model in which the methods of Chapter 3 as well as those of Chapter 2 can be displayed, I shall look at a model even simpler than those discussed at the end of Chapter 2. A popular instantaneous model for the population growth of a single species, distributed homogeneously in space and having a finite upper limit to growth, is the logistic equation

Biochemical Oscillator Model

\frac{{dx}}{{dt}} = rx\left( {{{1 - x} \mathord{\left/ {\vphantom {{1 - x} K}} \right. \kern-\nulldelimiterspace} K}} \right)

Predation Models of the Volterra Type

(1) .

Synthesis and crystal structure of zinc-vanadium complex [ZnII(LH3)(L)VIV][PF6]3 [LH3 = N,N',N''-tris(2S)-2-hydroxypropyl-1,4,7-triazacyclononane]: a chiral mixed-metal pendant-arm macrocyclic dimer containing nonvanadyl vanadium(IV)

The bone marrow contains stem cells which proliferate and also differentiate into precursors of the various types of blood cell, such as the erythrocytes (red cells) the granulocytes, and the monocytes (types of white cell). The maturing time in the marrow is for example about ten days for granulocytes and about three days for monocytes. In the case of monocytes further development takes place. These cells pass through the blood stream into tissue in about one day, and turn into macrophages. The number of cells of each type that are produced in the marrow of a healthy individual is adapted to the requirements of the body, red cell production being related to the need of tissues for oxygen, and white cell production to the need for defense against infection. General surveys of the topic of blood cell production, or haemopoiesis, can be found in the books by Metcalf and Moore (1971), Cline (1975) and Wickramasinghe (1975).

Potential radiation-pressure-induced instabilities in cavity interferometers.

Sequences of biochemical reactions in which the end product inhibits the first reaction are not uncommon. They represent a rather simple way of controlling the amount of the end product formed, and arguments can be given [Savageau (1976)] to show that this particularly simple feedback loop has advantages over other possible modes of control. One rarely has sufficiently detailed data to attempt to build a model for a specific sequence of this kind, and quite a lot of work has been in terms of a schematic general model due to Goodwin (1965). In this model all the reactions have linear kinetics, except for the inhibition process. Goodwin suggested that in his model the negative feedback should lead to oscillations. Early work was mainly numerical, but in the last few years a considerable degree of progress has been made in the analytical study of periodic solutions of the equations of the model. For a comprehensive review see Tyson and Othmer (1978).