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50 Chapter 3
3.2 Elaboration of Ru II,II analog of [M3(BTC)2]n
The results summarized in this Chapter 3.2 are initial studies directed to solve the
remaining issues mentioned in Chapter 3.1 and to target Ru II, II analog of [M3(BTC)2]n.
The study mentioned earlier (in Chapter 3.1) involving the investigation of Ru II,III analogs
of HKUST-1 shows rather a complicated picture. As described, the residual acids and the
inevitable counter-ions in the frameworks, to some extent, obstruct the porosity of the
Ru-MOFs. One can imagine that the catalytic activity and the sorption properties of these
materials can be definitely enhanced if the CUSs could be fully available without the
additional coordination (“blocking”) by the counter-ions Y (Cl - , F - , OH - or AcO - , etc.). The
pre-activation procedure (i.e. solvent exchange) helps largely to decrease the
concentration of the incorporated guest molecules such as acetic acid. Getting rid of the
acetic acid as well as the counter-ions are indeed of great importance to elaborate Ru II,II
analog of [M3(BTC)2]n in which the Ru-centers would be the same (in terms of oxidation
state and coordination geometry) as Cu sites in Cu-HKUST-1. One approach to improve
the situation could be the strict exclusion of any additional carboxylic acid as component
of the solvothermal reaction medium. Acid catalysis seems to be needed to facilitate the
coordination equilibria and kinetics of the substitution chemistry at the Ru-centres.
However, every attempt in this direction has not been successful so far (Figure 7.12). On
the other hand, the requirement of avoiding the substitution inert mixed valence Ru II,III -
SBUs for CSA and moving to the Ru II,II -SBUs as well as the strict exclusion of redoxchemistry
(inert conditions) together with any source of coordinating counter-ions Y is
another way to sort out the complexity of the coordination environment (i.e. mixed
valences of Ru centers, residual acids from the starting reactant-solvent and/or the
starting precursors) of the Ru-analogs of HKUST-1.
3.2.1 Synthesis and characterization of SBU-e and Ru-MOF 5
Ru II,II -SBU ([Ru2(OOCCH3)4],SBU-e) was obtained from a blue solution of ruthenium(III)
chloride according to the reported method. [206] The cell parameters obtained from the
single crystal XRD measurements of [Ru2(OOCCH3)4](THF)2 (crystallized from the hot
THF solution) are in a good agreement with the corresponding values communicated in
the literature (Table 7.2). [207] As appeared, prepared complex is air sensitive and loses its
crystallinity after solvent de-coordination. Nonetheless, the FT-IR bands of the symmetric