The crystal structure of the deuterated Tutton salt (ND 4 ) 2 [Cu(D 2 O) 6 ](SO 4 ) 2 determined by X-ray diffraction at several temperatures between 100 and 321 K is reported. The intermediate and longest Cu-O bond lengths of the Jahn-Teller distorted octahedral Cu(D 2 O) 6 2+ ion progressively converge as the temperature is raised above ∼200 K, and this is accompanied by a partial rotation of the ammonium and sulfate groups. The g-values derived from the EPR spectrum of the compound exhibit similar behavior, as do those of ∼1% Cu 2+ doped into the isomorphous zinc(II) compound. The temperature dependence of the g-values of Cu 2+ -doped (ND 4 ) 2 [Zn(D 2 O) 6 ](SO 4 ) 2 may be interpreted satisfactorily by a model which assumes a Boltzmann thermal distribution between two energy states which differ solely in the orientation of the Cu(D 2 O) 6 2+ ion in the lattice. However, such a model does not satisfactorily explain the behavior of pure (ND 4 ) 2 [Cu(D 2 O) 6 ](SO 4 ) 2 , and it is suggested that this is due to cooperative interactions. A new model, in which the probable energy state of each complex is estimated after taking into account the likely orientations of its neighbors in the lattice, is described. Application of this model suggests that the thermal behavior is dominated by the cooperative interactions between complexes, these being transmitted via the hydrogen-bonding network. Comparisons are drawn with the cooperative interactions observed in more strongly coupled Jahn-Teller systems and in compounds for which the structural changes are associated with equilibria between two spin states.

The first example of a pressure-induced Jahn-Teller distortion switch has been observed in a single-crystal time-of-flight neutron diffraction study of the Tutton salt ( N D~)~[ C U ( D Z O )~] ( S~~)~ at T = 15 K, P = 1 bar (h) and T = 15 K, P = 1.5 kbar (h). Also studied was the hydrogenous salt ( N H~)~[ C U ( H~O )~] ( S O~)~ at T = 14 K, P = 1.4 kbar (HH). The unit cell parameters are as follows: h, a = 9.451(2) (2), Z = 2, V = 674.5(2) A3, space group = P21/a. Application of 1.5 kbar of pressure to the deuterated crystal produces a decrease in the lengths of the a and b axes by 0.315(2) and 0.451(4) A, respectively, whereas the c axis increases by 0.275( 1) A. Comparison of the 4. and L~H structures shows that the long axis of the Jahn-Teller distortion has switched by 90°, Le., Cu(l)-0(7) = 2.022(2) and Cu(1)-O(8) = 2.310(2) A for 4. vs Cu(1)-0(7) = 2.290(2) and Cu(1)-O(8) = 2.014(2) A for h, so that the DH and HH structures are similar. For HH Cu(1)-0(7) = 2.272(2) and Cu(1)-O(8) = 2.005(2) A. The switching of the long axis of the Jahn-Teller distortion appears to be associated with the rotation of the ND4+ ion with a concomitant change in the hydrogen bonding of the coordinated water molecules with the S042-ions. The resulting adiabatic potential energy surfaces are calculated using tetragonal and orthorhombic strain parameters estimated from the

The crystal structures of [Cu,(bipyam-H),CI,]-H,O (I ) and [Cu,(bipyam-H),Br,]-H,O (2) where bipyam-H = bis(2-pyridyl)amide, have been determined by X-ray analysis, in the orthorhrombic space group Pnn2: ( I ) , a = 14.092(3), b = 12.895(3), (c) = 1 1 .I 90(2) A, Z = 2, and R = 0.032 for 2 453 observed and 2 029 unique reflections; (2), a = 14.1 86(3), b = 13.040(3), c = 11.31 3(2) A,

The crystal structures of (ND4)2[Cu(D2O)6](SO4)2 at 295 K, determined by X-ray diffraction at pressures of 1 bar, ∼1.5 kbar and ∼3.0 kbar, are reported. Between 1 bar and 1.5 kbar, the crystal structure changes to one almost identical to that of the corresponding hydrogenous compound at 1 bar. The structural change involves a 90° switch in the direction of the long bonds of the Cu(D2O)6 2+ ion, accompanied by a change in the hydrogen-bonding interactions of the ammonium cations. Comparison of these two structures with those at ∼15 K shows that at room temperature, for both the high (H) and low (L) pressure phases, the Cu complexes are in thermal equilibrium with the other structural isomer. Though one of these is energetically preferred in the H and the other in the L phase, the variation of the powder EPR spectrum with pressure indicates a continuous transition between both within ∼1 kbar and suggests that at ∼0.5 kbar the two orientations of the copper complex are similar in energy. However, the underlying thermally induced equilibrium is little affected by pressure, and this is also the case for the Cu(H2O)6 2+ ion in Cu2+-doped K2[Zn(H2O)6](SO4)2. The crystal structure of K2[Cu(H2O)6](SO4)2 at 15 K and 1.4 kbar, determined by time-of-flight neutron diffraction, is similar to that at 295 K and 1 bar, except for indications that here also a thermal population of the higher energy form in which the directions of the long and intermediate Cu−O bonds interchange occurs at 295 K. The powder EPR spectrum of the potassium salt at 295 K shows little change between 1 bar and 11 kbar.

On the basis of recently reported abyssinone II and olympicin A, a series of chemically modified flavonoid phytochemicals were synthesized and evaluated against Mycobacterium tuberculosis and a panel of Gram-positive and -negative bacterial pathogens. Some of the synthesized compounds exhibited good antibacterial activities against Gram-positive pathogens including methicillin resistant Staphylococcus aureus with minimum inhibitory concentration as low as 0.39 μg/mL. SAR analysis revealed that the 2-hydrophobic substituent and the 4-hydrogen bond donor/acceptor of the 4-chromanone scaffold together with the hydroxy groups at 5- and 7-positions enhanced antibacterial activities; the 2′,4′-dihydroxylated A ring and the lipophilic substituted B ring of chalcone derivatives were pharmacophoric elements for antibacterial activities. Mode of action studies performed on selected compounds revealed that they dissipated the bacterial membrane potential, resulting in the inhibition of macromolecular biosynthesis; further studies showed that selected compounds inhibited DNA topoisomerase IV, suggesting complex mechanisms of actions for compounds in this series.