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A series of 4-substituted methoxylbenzoyl-aryl-thiazoles (SMART) have been discovered and synthesized as a result of structural modifications of the lead compound 2-arylthiazolidine-4-carboxylic acid amides (ATCAA). The antiproliferative activity of the SMART agents against melanoma and prostate cancer cells was improved from μM to low nM range compared with ATCAA series. The structure-activity relationship was discussed from modifications of "A", "B" "C" rings and the linker. Preliminary mechanism of action studies indicated that these compounds exert their anticancer activity through inhibition of tubulin polymerization.

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Biphenylene dimers, which may be considered as "macrocyclic" 2 × 2 fragments of net 1 and dimeric fragments of a double-stranded polymer, 5, are prepared. X-ray crystallography on two polymorphs of the dimer 9 reveals that its bond alternation is analogous to that in biphenylene; the tetraphenylene part of 9 has approximately C 2h symmetry with a small dihedral angle (<12°) between the benzene rings in the adjacent biphenylenes. Cyclic voltammetry of 9 gives two reversible waves corresponding to a radical anion and a dianion; the lithium and potassium salts of these anions, 9 •-,M + (M ) Li, K) and 9 2-,2M + (M ) Li, K), were generated and characterized by ESR, NMR, and UV-vis spectroscopies. The spectral data for the dianions are compatible with classical structures; no evidence for "in-plane aromaticity" is found. For polymer 5, a localized band and large density of states near the Fermi level are found, using extended Hu ¨ckel theory calculations.

Two, bifunctional side-chain cyclopentadienylmanganese tricarbonyl complexes, 7 (pyridine and ketone side chain) and 14 (thioamide and pyridine side chain), were prepared and converted to chelates following CO dissociation by UV irradiation. Both pyridine (8) and carbonyl (9) chelates are observed following irradiation of 7. In contrast, only thioamide chelate ( 16) is observed following irradiation of 14 even though a pyridine group was available. Visible irradiation isomerizes the pyridine chelate 8 to the carbonyl chelate 9, which thermally isomerizes back to 8 at 25 °C in a few minutes, demonstrating a photochromic response from a cyclopentadienyl-manganese complex based on a linkage isomerization of a tethered functional group. DFT calculations predicted that the activation enthalpy of thermal linkage isomerization would be 20.8 kcal/mol and that the mechanism is likely an associative process that does not involve a simple dissociation of the manganese bond to the side-chain ketone. The DFT calculations were supported by subsequent dynamic NMR experiments that yielded an activation enthalpy and entropy of 21.4 ( 0.8 kcal/mol and 3.5 ( 0.1 eu, respectively. The studies indicate that a compound with a tethered, coordinated functional group, which is otherwise not labile, can isomerize by a low-energy pathway if there is an appropriate "conduit" to another functional group with a stronger metal-ligand bond. Thus, the preparation of photochromic organometallic complexes based on linkage isomerization will require a bridge that inhibits an associative walk between functional groups if they are to be bistable.

NiA120 4 is a largely inverse spinel, which in detail shows increasing randomisation with temperature of Ni and A1 between the octahedral and tetrahedral cation sites of the spinel structure. We have used powder XRD to determine this cation distribution in various samples of NiA120, quenched after annealing between 700 and 1400 ~ C. The inversion parameter (x) can be measured with a precision of ___ 0.004 (one standard deviation), and a comparison of different methods of synthesis, X-ray diffraction and refinement techniques, suggests a probable accuracy of better than 0.01. The results are supported by some preliminary single crystal refinements on flux-grown samples.Below 800~ the rate of cation ordering becomes very slow, and, despite reaching an apparently steady state, it is doubtful if our samples attained complete internal equilibrium. Above 1250 ~ C the cation redistribution becomes so fast that the quenching method becomes unreliable. Between 800 and 1250~ C inclusive, the degree of inversion changes smoothly from 0.87 at 800 ~ C to 0.79 at 1250 ~ C, and is accompanied by linear changes in u, the oxygen parameter, from 0.2555 to 0.2563 (+0.0002), and ao, the lattice parameter, from 8.0462 to 8.0522 ~ (_ 0.0002 ~).If no non-configurational entropy of disordering is assumed, the change of x with temperature can be described by a non-linear enthalpy of disordering model (O'Neill and Navrotsky 1983, 1984) with ~Ni-A1= 17.5 _ 2.3, fi = --18.4___ 1.4 kJ/g-atom. The fi term thus agrees with the -20 k J/g-atom suggested for all 2 3 spinels by O'Neill and Navrotsky (1984). However, if the expected electronic entropy of Ni 2 + in tetrahedral co-ordination is included (9.13 J/K g-atom), a very different best fit value of fi= +8.3 kJ/mol is obtained. The present data, despite their precision, cannot be used to distinguish between these alternative models.

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