The intense interactions of guest molecules with the pore walls of nanoporous materials is the subject of continued fundamental research. Stimulated by their thermal energy, the guest molecules in these materials are subject to a continuous, irregular motion, referred to as diffusion. Diffusion, which is omnipresent in nature, influences the efficacy of nanoporous materials in reaction and separation processes. The recently introduced techniques of microimaging by interference and infrared microscopy provide us with a wealth of information on diffusion, hitherto inaccessible from commonly used techniques. Examples include the determination of surface barriers and the sticking coefficient's analogue, namely the probability that, on colliding with the particle surface, a molecule may continue its diffusion path into the interior. Microimaging is further seen to open new vistas in multicomponent guest diffusion (including the detection of a reversal in the preferred diffusion pathways), in guest-induced phase transitions in nanoporous materials and in matching the results of diffusion studies under equilibrium and non-equilibrium conditions.

The molecular structure of aluminium and iron(III) complexes with 3-phenyl and 3-(4-pyridyl) (HL) substituted acetylacetonate ligands is appreciably distorted. For AlL3 and FeL3 this shows that the orientation of the side pyridyl-N donor atoms lone pairs is about 90 and 135 degrees which favours the assembly of heterobimetallic square patterns in Al(Fe)L3 complexes with metal ions. This was employed for the modular construction of semi-regular heterobimetallic networks, in which the pyridyldiketonate ligands bridge pairs of Fe(Al)/Cd(Co) metal ions and support the structure of 1D and 2D coordination polymers. The unprecedented 2D structure of [Cd[AlL3](CH3OH)[NO3]2].2CHCl3 and Cd[AlL3](CH3OH)Br2].2CHCl3 . 2CH3OH is based upon plane tiling by a set of heterobimetallic squares and octagons, while [Cd[FeL3]2(NO3)2].2H2O and [Co[AlL3]2Cl2].4CHCl3 . 2CH3OH are 1D polymers and exist as chains of heterobimetallic squares sharing opposite vertices.

The dilithium salts of N,N′,N′′-tris(trimethylsilyl)diethylenetriamine (1), N-methyl-N′,N′′bis(trimethylsilyl)diethylenetriamine (2), and N-methyl-N′,N′′-bis(diisopropyl)diethylenetriamine (3) reacted in THF, at -40 °C, with AlCl 3 affording monomeric aluminum chloride derivatives 4 (55% yield), 5 (76% yield), and 6 (71% yield), respectively. Addition of 1 equiv of AlMe 3 to the amine 2 gave rise to the five-coordinate dimethylaluminum derivative 9 (67% yield); heating a toluene solution of 9 overnight at 80 °C induces a loss of methane giving rise to the four-coordinate methylaluminum compound 10 (50% yield). The amine 2 also reacted at low temperature with LiAlH 4 affording derivative 11 (38% yield). Compounds 4-6 reacted subsequently in toluene with 1 equiv of HCl and 1 equiv of AlCl 3 to afford the first chiral tetracoordinated aluminum cations 12 (94% yield), 13 (93% yield), and 14 (90% yield), respectively. Single-crystal X-ray diffraction studies of derivatives 4, 5, 8, 10, 11, 12, and 15 have been carried out. They revealed that the tridentate nitrogen donors enforce an approximately trigonal-monopyramidal coordination geometry for neutral and cationic four-coordinate aluminum complexes. All cationic aluminum derivatives 12-14 and the neutral aluminum chloride 4 brought about the oligomerization of propylene oxide (PO). Low molecular weight polymers having narrow molecular weight distributions were obtained. The 13 C NMR spectra of these polymers indicate that they consist exclusively of head-to-tail linkages and that these macromolecules are rich in meso diad and isotactic triad sequences. Due to the presence of a free axial site, a new mechanism for PO polymerization is proposed. Methyl-and hydridoaluminum derivatives 10 and 11, as well as aluminum alkoxide, prepared in situ by reacting derivative 13 with PO, initiated the polymerization of (D,L)-lactide in benzene at 80 °C. High molecular weight polymers of broad molecular weight distributions were obtained in good yields.

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