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Chapter 3 31<br />
In this Chapter CSA is employed to systematically study the factors of synthetic conditions<br />
affecting the overall structure, composition and properties (in particular, thermal<br />
stability, porosity, etc.) of the Ru-based HKUST-1 analogous compounds (Scheme 7.3).<br />
Various Ru precursors, namely [Ru2(OOCR)4X] and [Ru2(OOCCH3)4]A, in which R = CH3 or<br />
C(CH3)3; X = Cl; A = BF4 or BPh4, were adopted as starting materials in order to modify the<br />
properties of the obtained Ru-MOF samples while maintaining the isoreticular<br />
relationship to HKUST-1. Switching from the -CH3 to bulkier R-group (e.g. -C(CH3)3)<br />
should increase the solubility of the polymeric ruthenium precursors, and, subsequently,<br />
would influence the kinetics of the MOF synthesis (better/faster nucleation and growth).<br />
On the other hand, employing weakly coordinating anions (WCA), like [BF4] - or [BPh4] - ,<br />
may allow modulation of the CUS within the Ru-MOF. Utilizing these counter-ions, A<br />
avoids the formation of a polymeric (insoluble) structure of the Ru precursors on one<br />
hand. On the other hand, it is anticipated that A being less prone to be incorporated into<br />
the framework via coordination to the Ru II,III -centers and, thus, may be removed by<br />
washing and activation of the samples. Unless, note, that H2O is always around in the<br />
solvothermal reactions and formation of -OH and its incorporation as component X must<br />
be also considered even in case of using WCA A, such as BF4 or BPh4.<br />
3.1.3 [Ru3(BTC)2Yy]n·G g obtained by CSA using [Ru2(OOCR)4X] and<br />
[Ru2(OOCCH3)4]A: synthesis and characterization<br />
3.1.3.1 CSA-precursors<br />
The Ru-precursors ([Ru2(OOCR)4X] and [Ru2(OOCR)4]A were prepared according to the<br />
literature (Scheme 7.1). [199-202] Characterization of all precursors confirmed the<br />
compositions and structures being expectedly analogous to the reported compounds. All<br />
structures consist of Ru2-clusters coordinated by four carboxylic groups. Thus, this kind<br />
of binuclear units (PWs) are similar to the building units in the [Cu3(BTC)2]n framework,<br />
affording the idea to construct the isostructural [Ru3(BTC)2]n by means of the CSA. The<br />
PXRD patterns of [Ru2(OOCCH3)4Cl] (SBU-a, R = CH3) showed the phase-purity of the<br />
compound (Figure 7.3). [203] Furthermore, following the well documented literature<br />
method, single crystals of [Ru2(OOCC(CH3)3)4(H2O)Cl](CH3OH) (SBU-b, R = C(CH3)3) were<br />
obtained. The cell parameters and other crystal structure data of SBU-b are presented in<br />
Table 7.1 and Figure 7.5. To note, the obtained crystallographic data are of superior
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