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and most publications in the field deal with the evaluation of the catalytic activity of polyoxoanion salts (oxidation catalysis) or the free acids (acid catalysis) [3–5, 38]. Polyoxoanions have been shown to activate small molecules (e.g. O 2 , H 2 O 2 ) which are highly desired oxidants in the chemical industries for the catalysis of organic reactions (e.g. epoxidation, hydroxylation). Currently polyoxoanions are being used as catalysts in different processes on an industrial scale worldwide. Substitution of one or more addenda atoms by redox-active transition metal ions (e.g. Fe 3+ , Ru 3+ ) allows to fine tune the catalytic activity of polyoxoanions [39]. The interactions of polyanions with enzymes and other biomolecules is also being studied and it allows for a better understanding of the antitumor/viral activities of this class of compounds [40–42]. It is also possible to graft organic groups to the surface of the polyoxoanions via incorporation of an organo-metal (PhSn) or an organo non-metal (e.g. RSi)[43] fragment in a lacunary polyoxometalate precursor. The monoorgano tin chemistry of polyoxometalates has been studied mainly by Pope and by few other groups. It is known that the size, shape and charge density of many polyoxoanions are of interest for pharmaceutical applications. However, the mechanism of action of many polyoxoanions is not selective towards a specific target. In order to improve selectivity it appears desirable slightly to modify a given polyoxoanion core structure . However, such attempts frequently result in a different polyoxoanion framework. Therefore the most straightforward and promising approach towards systematic derivatization of polyoxoanions involves attachment of organic groups to the surface of the metal-oxo framework. In order to be attractive for pharmaceutical applications, the functionalized polyoxoanions should be water-soluble and fairly stable at physiological pH. To date the number of water-soluble polyoxoanions with tightly bound organic functionalities is rather small. Pope and co-workers [44–47] were the first to study the interaction of monoorganotin groups (e.g. n-C 4 H 9 Sn 3+ , C 6 H 5 Sn 3+ ) and polyoxoanions. They reacted different organotin halide precursors (e.g. n-C 4 H 9 SnCl 3 , C 6 H 5 SnCl 3 ) with a large number of lacunary heteropolytungstates in aqueous solution and they were able to identify novel (mostly dimeric) polyoxoanion structures. Single-crystal X-ray diffraction studies revealed that these compounds contain tightly anchored organotin fragments. The com- 15
Fig. 1.11: Monomeric (left) and dimeric species (right) of monoorganotin containing polyoxotungstates. pounds were also studied in solution by multinuclear NMR spectroscopy. This technique is also very valuable in the evaluation of the stability of polyoxoanions at physiological pH and low concentration for medicinal applications. Liu and coworkers [48–52] have also synthesized some monoorganotin substituted polyoxotungstates. They introduced ester functionalities to the organotin fragments and tested the biological (antitumor) activity of their products. Most recently, the groups of Pope and Hasenknopf showed independently that monoorganotin containing polyanions can be further derivatized by peptide or ester functions [53–55]. Haiduc et al. also reported on monoorganotin derivatives of polyoxotungstates [56]. However, the proposed structures of Liu and Haiduc need to be confirmed by X-ray diffraction. Interestingly, there were no reports on diorganotin substituted polyoxotungstates. Such species could allow for more flexibility for the interaction with and binding to other organic compounds and biomolecules. Therefore we investigated the interaction of di-organotin groups with the entire arsenal of lacunary polyoxotungstates. Introduction of organic groups into the POM framework could greatly increase the number of compounds available for screening, together with a potential modulation of essential features such as stability, bioavailability, recognition, etc [57]. While there is a signifi- 16
Page 1 and 2: Hybrid Organic-Inorganic Polyoxomet
Page 3 and 4: Abstract Polyoxometalates (POMs) ar
Page 5 and 6: the cubic system (space group I m¯
Page 7 and 8: AsW 9 O 32 OH) 2 ]·36H 2 O (RbNa-1
Page 9 and 10: Paris-Sud, Orsay Cedex, France) for
Page 11 and 12: 2.2.9 Synthesis of K 12 [H 2 P 2 W
Page 13 and 14: Bibliography . . . . . . . . . . .
Page 15 and 16: 3.5 Left: combined polyhedral and b
Page 17 and 18: 3.33 Combined polyhedron and ball/s
Page 19 and 20: List of Tables 1.1 Selected M-M dis
Page 21 and 22: MO 6 octahedra surrounding a centra
Page 23 and 24: 1.1.1 The clathrate-like structure
Page 25 and 26: 7(MoO 4 ) 2− + 8H + → [Mo 7 O 2
Page 27 and 28: Fig. 1.4: Combined polyhedral/ball
Page 29 and 30: This planar structure was originall
Page 31 and 32: [X 2 M 18 O 62 ] 6− , the D 3h We
Page 33: [P 2 W 19 O 68 (HO)] 14− , [P 2 W
Page 37 and 38: Chapter 2 Experimental 2.0.1 Reagen
Page 39 and 40: 2.2 Preparation of starting materia
Page 41 and 42: as Cs 6 [P 2 W 5 O 23 ]·7H 2 O by
Page 43 and 44: was adjusted between 5-6 by additio
Page 45 and 46: Chapter 3 Results 3.1 The hybrid or
Page 47 and 48: Fig. 3.2: FTIR spectra of compound
Page 49 and 50: Fig. 3.3: W 183 NMR spectra of (CsN
Page 51 and 52: Fig. 3.5: Left: combined polyhedral
Page 53 and 54: formed upon crystallization and bot
Page 55 and 56: X-ray Crystallography A crystal of
Page 57 and 58: the presence of the four (CH 3 ) 2
Page 59 and 60: Fig. 3.10: Cyclic voltammogram of 2
Page 61 and 62: as a function of electrolyte compos
Page 63 and 64: was observed that could be traced t
Page 65 and 66: electrochemical set-up was an EG &
Page 67 and 68: Fig. 3.14: The central core of Sn(C
Page 69 and 70: of these fragments [88, 90]. For co
Page 71 and 72: diffractometer using Mo K α radiat
Page 73 and 74: Fig. 3.18: Side view of [{Sn(CH 3 )
Page 75 and 76: host−guest systems with large cav
Page 77 and 78: X-ray Crystallography Single crysta
Page 79 and 80: 3.5.2 Results and discussions Polya
Page 81 and 82: Fig. 3.26: Ball and stick represent
Page 83 and 84: can distinguish between different m
Page 85 and 86:
Fig. 3.28: STM pictures of {Sn(CH 3
Page 87 and 88:
Fig. 3.31: Size distribution by int
Page 89 and 90:
3.6 The bis-phenyltin substituted,
Page 91 and 92:
Table 3.7: Crystal Data and Structu
Page 93 and 94:
tral belt in-between the two tin at
Page 95 and 96:
Fig. 3.35: 183 W NMR spectra of com
Page 97 and 98:
whereas they are five-coordinated (
Page 99 and 100:
investigated by scanning tunneling
Page 101 and 102:
3.8 The di-titanium substituted, lo
Page 103 and 104:
Fig. 3.37: Ball/stick (left), polyh
Page 105 and 106:
[As 2 W 19 O 67 (H 2 O)] 14− , [A
Page 107 and 108:
3.9 The cyclic trimeric-titanium su
Page 109 and 110:
Table 3.9: Crystal Data and Structu
Page 111 and 112:
Fig. 3.40: FTIR spectra of compound
Page 113 and 114:
Fig. 3.42: Side-view of compound 11
Page 115 and 116:
11 by 183 W-NMR (at 16.66 MHz on a
Page 117 and 118:
3.11 Structure and solution propert
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472(w), 444(w) cm −1 . This proce
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MHz in 10 mm tubes and the 111 Cd N
Page 123 and 124:
Fig. 3.47: 111 Cd NMR spectra of [C
Page 125 and 126:
in aqueous solution, so that the nu
Page 127 and 128:
of cadmium ions in 12 and 13 and it
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doubtedly 183 W-NMR, but the parama
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K): (relative intensities in parent
Page 133 and 134:
Fig. 3.49: Combined polyhedral/ball
Page 135 and 136:
Fig. 3.50: 183 W NMR spectrum of [I
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(17) are isostructural. They consis
Page 139 and 140:
Fig. 3.53: 183 W NMR spectrum of [I
Page 141 and 142:
3.12.4 Conclusion We have synthesiz
Page 143 and 144:
[37] D. Gatteschi, O. Kahn, J. Mill
Page 145 and 146:
94:226403, 2005. [123] R. J. Hamers
Page 147 and 148:
[206] I. Loose, E. Droste, M. Bösi
Page 149 and 150:
NMR Spectra Fig. 3.54: 13 C NMR spe
Page 151 and 152:
Fig. 3.56: 31 P NMR spectrum of pol
Page 153 and 154:
Fig. 3.58: 13 C NMR spectrum of pol
Page 155 and 156:
Fig. 3.60: 1 H NMR spectrum of poly
Page 157 and 158:
Fig. 3.62: 119 Sn NMR spectrum of p
Page 159 and 160:
Fig. 3.66: 1 H NMR spectrum of poly
Page 161 and 162:
Fig. 3.70: 13 C NMR spectrum of pol
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were applied and an absorption corr
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Fig. 3.75: Size distribution by num
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Table 3.16: Crystal Data and Struct
Page 169 and 170:
Fig. 3.80: FTIR spectra of compound
Page 171 and 172:
FIRASAT HUSSAIN International Unive
Page 173 and 174:
Publications 1. Observation of a Ha
Page 175 and 176:
PAPERS IN CONFERENCE/ SYMPOSIA / WO
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