Built to order: molecular tinkertoys from the [Re(6)(mu(3)-Se)(8)](2+) clusters

Ligand substitution of [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CH(3)CN)](SbF(6))(2) (1) with pyridyl-based ligands, 2,4,6-tri-4-pyridyl-1,3,5-triazine (L1) and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (L2), produced respectively the star-shaped tricluster (T1) and tetracluster (T2) arrays, wherein three (T1) and four (T2) units of the [Re(6)(mu(3)-Se)(8)](2+) core-containing clusters are interconnected by the corresponding bridging ligands. These novel supramolecular assemblies were characterized by a combination of NMR ((1)H and (31)P) spectroscopy, ESI-MS, and microanalysis. The molecular and solid-state structures of T1 have also been established by single-crystal X-ray diffraction.     

Isomer-specific spectroscopy and conformational isomerization energetics of o-, m-, and p-ethynylstyrenes

The infrared and ultraviolet spectroscopy of o-, m-, and p-ethynylstyrene isomers (oES, mES, and pES) were studied by a combination of methods, including resonance-enhanced two-photon ionization (R2PI), UV-UV hole-burning spectroscopy (UVHB), resonant ion-dip infrared spectroscopy (RIDIRS), and rotationally resolved fluorescence excitation spectroscopy. In addition, the newly developed method of stimulated emission pumping-population transfer spectroscopy (SEP-PTS) was used to determine the energy threshold to conformational isomerization in m-ethynylstyrene. The S(1) <-- S(0) origin transitions of oES and pES occur at 32 369 and 33 407 cm(-1), respectively. In mES, the cis and trans conformations are calculated to be close in energy. In the R2PI spectrum of mES, the two most prominent peaks (32672 and 32926 cm(-1)) were confirmed by UVHB spectroscopy to be S(1) <-- S(0) origins of these two conformers. The red-shifted conformer was identified as the cis structure by least-squares fitting of the rotationally resolved fluorescence excitation spectrum of the origin band. There are also two possible conformations in oES, but transitions due to only one were observed experimentally, as confirmed by UVHB spectroscopy. Density functional theory calculations (B3LYP/6-31+G) predict that the cis-ortho conformer, in which the substituents point toward each other, is about 8 kJ/mol higher in energy than the trans-ortho isomer, and should only be about 5% of the room temperature population of oES. Ground-state infrared spectra in the C-H stretch region (3000-3300 cm(-1)) of each isomer were obtained with RIDIRS. In all three structural isomers, the acetylenic C-H stretch fundamental was split by Fermi resonance. Infrared spectra were also recorded in the excited electronic state, using a UV-IR-UV version of RIDIR spectroscopy. In all three isomers the acetylenic C-H stretch fundamental was unshifted from the ground state, but no Fermi resonance was seen. The first observed and last unobserved transitions in the SEP-PT spectrum were used to place lower and upper bounds on the barrier to cis --> trans isomerization in m-ethynylstyrene of 990-1070 cm(-1). Arguments are given for the lack of a kinetic shift in the measurement. The analogous trans --> cis barrier is in the same range (989-1065 cm(-1)), indicating that the relative energies of the zero-point levels of the two isomers are (E(ZPL)(cis) - E(ZPL)(trans))= -75 to +81 cm(-1). Both the barrier heights and relative energies of the minima are close to those determined by DFT (Becke3LYP/6-31+G) calculations.     

Synthesis of a novel 8-thia-1,4-diazacycl[3.3.2] azine

A unique covalently hydrated cyclazine adduct, 2-imino-6a-hydroxy-4,5,6,6a-tetrahydro-7H-8-thia-J, 4-diazacycl[3.3.2]azin-5-one hydrochloride was prepared by reacting ethyl 4-chloro-acetoacetate with 4,6-diamino-2-thiopyrimidine in neutral alcohol. Neutralization gave 2-imino-5,6a-dihydroxy-6,6a-dihydro-7H-8-thia-1,4-diazacycl[3.3.2]azine which decomposed to 4,6-diamino-2-acetonylthiopyrimidine upon heating in water. Warming the hydrated hydrochloride in concentrated hydrochloric acid caused dehydration to yield 2-imino-5-hydroxy-6H-8-thia-1,4-diazacycl[3.3.2]azine hydrochloride. Partial isomerization (20%) to 2-imino-5-hydroxy-7H-8-thia-1,4-diazacycl[3.3.2]azine hydrochloride occurred during recrystallization from aqueous acidic methanol. The free base, 2-imino-5-hydroxy-7H-8-thia-1,4-diazacycl[3.3.2]azine was obtained after neutralizing either of the tautomeric hydrochlorides. Treating the free base with trifluoroacetic acid produced a mixture of the trifluoroacetate salts of the two tautomeric bases. Isomerization of one trifluoroacetate salt into the other in trifluoroacetic acid was observed by pmr at room temperature. Both 2-amino-5-hydroxy-7-nitroso-8-thia-1,4-diazacycl[3.3.2]azine and 2-amino-5-hydroxy-6-nitroso-8-thia-1,4-diazacycl[3.3.2]azine were isolated after nitrosation of the hydrochloride mixture.     

Urological malignancies and the proteomic-genomic interface

The urological malignancies, renal, bladder and prostate cancer, account for approximately 16% of all cancer cases. Unfortunately 5-year survival rates are relatively poor, largely a result of many cases not being diagnosed before the tumour has metastasised. There is a clear need for the identification of markers which will allow earlier detection of disease, and predict prognosis and response to therapy. In addition, they may be of use as therapeutic targets. Current advances in molecular biology are allowing the identification of a number of tumour-associated changes which could be of clinical use in the future. However, with the rapid technological advances being made in the field of proteomics, this approach could be integrated with genomics providing a complementary alternative, overcoming disparities between mRNA levels and protein production, and additionally allowing the identification of tumour-associated post-translational modifications. These approaches have already been used to identify novel genes and other cancer-related changes involved in the pathogenesis of urological malignancies. This review describes current progress in the genomic and proteomic study of urological malignancies, and highlights the potential of using proteomic technologies in the study of this group of diseases.     

The Coordination and Transformation of Arene Rings by Transition Metal Carbonyl Cluster Complexes

A survey of the synthetic pathways and of the reactivity and catalytic activity of transition metal carbonyl clusters substituted with benzyne (and, for comparison, benzene and diene) ligands is given. Cluster-surface analogies are helpful in gaining an understanding of the homogeneous and heterogeneous catalytic behaviour of the clusters.     

A role for cryptochromes in sleep regulation

Background  

The cryptochrome 1 and 2 genes (cry1 and cry2) are necessary for the generation of circadian rhythms, as mice lacking both of these genes (cry1,2 ^-/-) lack circadian rhythms. We studied sleep in cry1,2 ^-/- mice under baseline conditions as well as under conditions of constant darkness and enforced wakefulness to determine whether cryptochromes influence sleep regulatory processes.     

ESR studies on the structure of C6F−6 anions

Rigid solution spectra for C₆F^?₆ and C₄F^?₈ are compared, and it is concluded that C₆F^]t-₆ cannot have the planar, σ^* structure previously postulated. Instead, a puckered-ring structure with σ and pseudo π delocalisation is postulated.     

Flexing the muscles of m-divinylbenzene: direct measurement of the barriers to conformational isomerization

The energy thresholds to isomerization of the three conformational isomers of m-divinylbenzene (cis-cis, cis-trans, and trans-trans) were directly measured by stimulated emission pumping-population transfer (SEP-PT) spectroscopy. The experimentally determined isomerization thresholds are Ethresh(cc --> ct, tt) = 1080-1232 cm(-1), Ethresh(tt --> ct, cc) = 1130-1175 cm(-1), Ethresh(ct --> cc) = 997-1175 cm(-1), and Ethresh(ct --> tt) = 997-1232 cm(-1). On the basis of the threshold values for X --> Y and Y --> X isomerization, the relative energies of the conformational isomers are -102 < or = E(ct) < or = +178 cm(-1) and -102 < or = E(cc) < or = +95 cm(-1) relative to E(tt) = 0. UV-hole-filling (UVHF) spectroscopy was also used to determine the effect of population returning to the ground state via fluorescence. A full set of governing equations for SEP-PT and UVHF spectroscopy is reported that will be generally useful for future studies using these methods. By comparison of these results with the computed stationary points on a calculated surface (DFT B3LYP/6-31+G*), the isomerization pathway was determined to involve sequential isomerization of each vinyl group rather than concerted motion. The energy thresholds were also combined with the ground state torsional vibrational energy levels to obtain a new fitted two-dimensional torsional potential for mDVB.