The [Cu-2(O2CMe)(4)(btd)(2)] complex as a bridging unit: preparation, characterisation, X-ray structure and magnetism of the 2D coordination polymer [Cu-6(O2CMe)(8)(OMe)(4)(btd)(2)](n) (btd=2,1,3-benzothiadiazole)

{A systematic investigation of the {[}Cu-2(O2CMe)(4) (H2O)(2)]/btd reaction system is described, where btd = 2,1,3-benzothiadiazole. Reaction of {[}Cu-2(O2CMe)(4)(H2O)(2)] with 5-8 equiv. of btd in both MeCN and MeOH yields {[}Cu-2(O2CMe)(4)(btd)(2)] (1) in 40-50\% yields. Treatment of {[}Cu-2(O2CMe)(4)(H2O)(2)] With 1.4 or 0.7 equiv. of btd in MeOH leads to the precipitation of the polymeric compound \{{[}Cu-6(O2CMe)(8)(OMe)(4)(btd)(2)]\} (2) in 82\% yield. Reaction of 1 with two equivalents of {[}Cu-2(O2CMe)(4)(H2O)(2)] in MeOH under reflux provides an additional route to 2. The structure of 1 consists of centrosymmetric dinuclear {[}Cu-2(O2CMe)(4)(btd)(2)] molecules of the paddle-wheel cage type. The two Cu-II ions are bridged by four eta (1):eta (1):mu (2) acetates, while a monodentate btd is at the apex of the square pyramid of each metal centre. The 2D structure of 2 consists of chains of tetranuclear, planar Cu-4(OMe)(4)(O2CMe)(4) repeating units running along the a axis, which are connected along the cell body diagonal via Cu-2(O2CMe)(4)(btd)(2) paddle-wheel dinuclear units. The btd molecules behave as bidentate bridging ligands. Within the tetranuclear units, each Cu-II ion is connected via two acetate bridges with one neighbouring Cu-II ion and via two methoxo bridges with the other neighbouring Cu-II ion; intertetranuclear linking is provided by two monoatomic acetate bridges. The results of solid state magnetic susceptibility studies are described for complex 2 in the temperature range 3-300 K. The results reveal antiferromagnetic exchange interactions between the Cu-II ions. The complicated structure of 2 does not permit an exact treatment for the determination of the various exchange interactions. However, an approximate 3-J magnetic model was constructed, resulting in an excellent fit. An orbital interpretation of the J-trend derived is also attempted. (C) 2001 Elsevier Science B.V. All rights reserved.

Assessment of the Typology and the Trophic Status of Two Mediterranean Lake Ecosystems in Northwestern Greece

The objective of this study is the assessment of the typology and the trophic relevant water quality parameters in two Mediterranean lakes (Lake Ziros and Lake Kastoria) under the view of the WFD. Lake types were identified based on characteristics specified in Annex II of the WFD, while trophic indexes (OECD, TSI Carlson) were used in order to assess their trophic status. A modified TSI index appropriate for warmer lakes was also applied. According to our results, Lake Kastoria is classified as eutrophic lake with a tendency to hypertrophication while Lake Ziros is a mesotrophic ecosystem with clear signals of eutrophication. Both ecosystems are considered "at risk" of not fulfilling the WFD environmental objectives due to the existence of certain anthropogenic pressures