Marie-Christine Labarre

On the conformational analysis of (CH3)3M (M = N, P, CH, SiH) molecules: CNDO/2 calculations versus experimental data. LEM or calder conformation?

Abstract CNDO/2 calculations are performed for the homogeneous series of (CH 3 ) 3 M compounds (M = N, P, CH, SiH) in order to determine the molecular equilibrium conformation. In agreement with available experimental data for the amine, the phosphine and the silane, the theoretical energy minimum is found for the (60, 60, 60) - so-called LEM - conformation in which each methyl group is staggered with respect to the two opposite (MC) bonds. The same LEM conformation is predicted to be theoretically preferred for the isobutane molecule, this result being very sensitive to the “C 3V or not” quality of the methyl groups. The values of optimized CMC angles, rotational barriers and dipole moments are well reproduced.

On the Scent of Dandelion Dendrimers. Part I. Cyclophosphazenic Hexapodanes as New Cores

Abstract Aminolysis of N3P3Cl6 by long-chain diamines, H2N—(CH2) n —NH2 (n  6), leads regiospecifically to hexadangling (or hexapodanes) monomeric species provided it was achieved on alumina impregnated with potassium hydroxide. These reactions run instantaneously at room temperature. Such hexapodanes constitute starting materials (cores) for future design of spherical (i.e. aesthetically similar to dry dandelion flowers) cyclophosphazenic dendrimers.

On the reliability of time-and-money non-consuming techniques for reaching real molecular structures in cyclophophazenes: NMR spectroscopy versus X-ray crystallography

Abstract An overall survey of 13 P NMR chemical shifts versus X-ray data for fifty kinds of cyclophosphazenic structures shows that NMR in solution is more reliable than crystallographic determinations for predicting how prone cyclophosphazenes are to generate new polymers.

On the scent of asymmetrical dandelion dendrimers: Part I. Starting materials from the regiospecific aminolysis of N3P3Cl6 by amino-alcohols

Abstract Starting materials for the design of asymmetrical dandelion dendrimers were synthesized upon the preliminary fixation of suitable amino-alcohols on hexachlorocyclotriphosphazene, N3P3Cl6, as “blockers”. Further linkage of diamines on solid supports leads to the expected asymmetrical moieties.

Lariat-bearing cyclophosphazenes: potential molecular sepulchers for magnetic resonance imaging agents

Abstract Lariat-bearing cyclophosphazenes were prepared by aminolysis of hexachlorocyclotriphosphazene with amino ester hydrochlorides followed by standard alkaline hydrolysis. These cryptands are actually capable of complexing gadolinium cations with stability constants larger than 10 28 ; this is much larger than the values for classical magnetic resonance imaging agents. Unfortunately, these cryptates are much too insoluble in physiological serum to be used for clinical purposes in a facile way.

ON THE SCENT OF SPHERICAL DENDRIMERS : CYCLOPHOSPHAZENIC DANDELION DENDRIMERS UP TO THE EIGHTH GENERATION

Abstract Preparation of spherical dendrimers up to the eighth generation from D3h cyclophosphazenic hexadangling cores (coded as sexapus) involves two repetitive steps: aminolysis of hexachlorocyclotriphosphazene, N3P3Cl6 0, by long-chain aliphatic diamines (such as 1,6-Diaminohexane and higher cousins) leading to sexapus cores with dangling diamino groups followed by a grafting of N3P3Cl5 flagstones as 5-fold growing multipliers on these amino endings. Dendrimers of the first (compounds 1a, b) to the eighth (compounds 8a, b) are described. Dendrimer of the eighth generation, 8b, possesses 2,343,750 terminal (P-Cl) functions (molecular weight 228,977,179).

On the Scent of Dandelion Dendrimers. Part IV. Molecular Modeling of Cyclophosphazenic Dandelion Dendrimers Up to the Fourth Generation

We recently reported on the neat synthesis of 3-dimensional, 6-functional cyclophosphazenic cores through a regiospecific peraminolysis of N3P3Cl6 by long-chain diamines on suitable solid supports. Preparation of spherical dendrimers (up to the eighth generation) from such cores was achieved through alternate additions of N3P3CI5 flagstones (5-fold multiplier) and of diamino tentacles (linker). The eighth generation possesses 2,343,750 terminal (P-CI) functions (M228,977,179), which are suitable for further nucleophilic substitutions. Molecular modeling shows that the compactness of these dendrimers is extremely low, conferring to these huge monomers a noticeable vacuity for accomodation of host moieties.

An answer to the SPIRO versus ANSA dilemma in cyclophosphazenes Part XVIII. The structure of the simplest ANSA derivatives, N3P3Cl4[HN(CH2)2O] and N3P3Cl3(CH3)[HN(CH2)3O]: molecular modeling versus X-ray

Abstract Molecular modeling is evidenced as a convenient tool for assigning the molecular structure of ANSA cyclophosphazenes.

Why “Spherical” Cyclophosphazenic Dandelion Dendrimers Have a Dipole Moment?

Molecular Modelling of “spherical” cyclophosphazenic dandelion dendrimers shows that the whole moieties belong to the C3 point group, conversely to the starting material, N3P3Cl6, which is of D 3h symmetry. Moreover, these spherical dendrimers actually have significant dipole moments due to a non-centrosymmetrical distribution of the lone pairs of the nitrogen atoms of their amino groups and functions.