Tuning Reactivity of Platinum(II) Complexes

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that of dinuclear Pt(II) complexes bridged by the flexible α,ω-alkyldiamine, with (CH2)n groups that have even numbers of carbon atoms. 24,25(b) The conformational differences significantly influenced the DFT calculated values of the Pt---Pt separation distances (through-space), i.e. Pt1 (12.07), Pt2 (13.74) and Pt3 (13.54 Å); and the dipole moments exhibited by Pt1 (1.93), Pt2 (4.01) and Pt3 (0.16 D) recorded in Table 6.2. These structural metrics are brought about by the smaller C–C (Å) bond length relative to that of S–S (Å) due to the larger size of S atom and also are influenced by the symmetry of the complex. These structural features together with the steric influences on the square-planar planes at the Pt(II) centres, as will be discussed later, are expected to control reactivity with the incoming nucleophiles. 6.3.5 Kinetic Measurements The substitution reactions of the complexes with thioureas (TU, DMTU, TMTU) and ionic nucleophiles (Br ¯ , I ¯ , SCN ¯ ) were carried out at pH 2.0. The purpose of keeping the solutions acidic was to make sure that the complex remains in aqueous form and at the same time protonate the released N-donor pyridyl bridging ligand so as to prevent it from re-coordination to the metal centre as shown in Scheme 6.4. Besides, protonation of thiourea (TU, pKa = -1.3) can be ruled out as reported recently. 46 As already mentioned, all the kinetic measurements were done under pseudo first-order conditions with respect to the nucleophile, in order to drive the reactions to completion. The results of the substitution reaction with bromide for all the studied complexes gave only one substitution process (Table 6.3) because of being a weak nucleophile. However, the substitution reactions of the aqua complexes with nucleophiles of stronger nucleophilicity like the thioureas (TU, DMTU, TMTU) and the other anionic nucleophiles (I ¯, SCN ¯) showed two reaction steps. The first step is attributed to simultaneous substitution of both aqua ligands by the nucleophiles. The second step is much slower by 1 to 3 orders of magnitude compared to the first step, and is assigned to the release of the linker following coordination of further nucleophiles to the Pt(II) centre. This conclusion is arrived at after monitoring the reaction between Pt1–Cl and TU (6 equiv.) by 1H NMR spectroscopy in DMF-d7. An array of the proton NMR spectra, showing the aromatic region only, is recorded in Figure 6.3. The adopted numbering system for the 15
pyridyl protons Ha/Hb used to monitor the progress of the reaction is shown on the structure of the Pt1–Cl complex as an inset in Figure 6.3. The signals of the coordinated ligand appear at Ha = 8.78 and Hb = 7.60 ppm as doublet resonances, which decreased during the reaction. After 1.5 h of the reaction, a broad singlet signal was observed at Ha* = 8.53 ppm, representing the released (free) pyridyl bridging ligand, because the excess thiourea displaces the last N-donor atom in the bridging system to produce [Pt(TU)4] +2 and/or any other undefined products. However, the Hb*-signal at 7.22 ppm for the second aromatic proton of the freed ligand was obscured by the broad peak due to thiourea, TU, at 7.20 ppm and is not shown on Figure 6.3. 9.0 8.9 8.8 Ha 8.7 8.6 8.5 Ha’ 8.4 8.3 8.2 ppm 16 8.1 DMF solvent Figure 6.3: The 1 H NMR spectra of the reaction of Pt1 with thiourea (2.0 mM) in DMF- d7, at 30 °C showing the release of the dps bridging ligand. Because of the low concentration of the Pt1–Cl complex, the aromatic resonances corresponding to the unreacted complex appears as downfield–shifted peaks as the reaction progressed. This is consistent with what has been reported before for bidentate coordinated Pt(II)-based DNA intercalators. 47 8.0 7.9 7.8 7.7 Hb 7.6 7.5 1.0 0.0 1.5 t/ h 2.0
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Tuning Reactivity of Platinum(II) C
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Declaration This thesis report is b
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Abstract Systematic kinetic and the
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Table of contents Acknowledgements
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2.5.5 Effect of Non-participating G
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5.2.1 Chemical and Solutions ......
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7.2 Experimental Section ..........
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procurements, Messers P. Forder and
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Figure 2.2 Potential energy profile
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Figure 4.6 Concentration dependence
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Figure 6.1 Spectrophotometric titra
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List of Tables Table 2.1 A selectio
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Table 6.4 Summary of rate constants
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TU thiourea DMTU 1,3-dimethyl-2-thi
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Table of Contents-1 Chapter 1 .....
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1.0 Introduction 1.1 Cancer Disease
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toxic potential. The most well-know
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1.3.2.2 Cellular Uptake Cisplatin i
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H 3N OH 2 Pt H 3N OH 2 Active Pt(II
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transformational pathways that comp
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the hydrolysis of the complex, wher
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1.3.4 Terpyridine Platinum(II) Comp
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H 3 N Cl Pt NH 3 H 3 N NH 2 (CH 2 )
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1.4 Kinetic Interest The platinum-b
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3. The effect of varying the positi
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17 R. A. Henderson, The Mechanism o
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Altona J. H. van Boom, G. A. van de
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76 (a)J. Kašpárková, J. Zehnulov
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Table of Contents-2 Chapter Two ...
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List of Tables Table 2.1: A selecti
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The mononuclear Pt(II) complexes 1-
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Potential Energy R + X RX 1 transit
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For the associative mechanism (A),
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the concentration of one of the rea
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k obs , s -1 0.00030 0.00025 0.0002
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k = Ae -Ea/RT 2.14 lnk = lnA - E a
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= 23.76 + R Hence, a plot of ln ⎛
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iii. # Δ V ≈ 10 cm3 mol-1 featur
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conventional methods are classical
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Figure 2.6: Schematic diagram of a
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The light transmitted from the samp
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c. Oxidizability: Ligands that are
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Table 2.1: A selection of n o pt va
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eaction with different nucleophiles
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eaction site from direct attack by
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PEt 3 PEt 3 R PEt 3 Pt Pt Y Y Cl R
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direct displacement of the leaving
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therefore, weaken the bond of the l
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σ-Donation According to classical
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References 1 (a) J. Reedijk, Chem.
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34 R. B. Jordan, Reaction Mechanism
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Table of Contents-3 Chapter 3.The
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Chapter 3 The π-Acceptor Effect in
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In order to extend our understandin
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after which water was added to quen
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O CH 3 + I + N O oH - N O O 7 CH 3
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84% (34.7 mg, 0.0618 mmol). 1 H NMR
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PhCN PhCN Pt Cl Cl + N N CH 3 N CH
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Complex Structure HOMO LUMO PtCl CH
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The geometry-optimised structures i
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against the concentration of the in
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Table 3.2: Summary of the second-or
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constants of CH3PhisoqPtCl decrease
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with π*-orbitals of the ligand. Th
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3.6 References 1 D. Rosenberg, L. V
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30 Microcal TM Origin TM Version 5.
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Figure S3.1: Kinetic trace at 448 n
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ln(k 2 /T) -6.0 -7.5 -9.0 -10.5 -12
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Table S3.3b: Average observed rate
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Table S3.5b: Temperature dependence
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Table S3.8: DFT calculated electros
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List of Figures Figure 4.1: Structu
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Table 4.2: Summary of pKa values fo
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4.1 Introduction Platinum compounds
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cis geometry, leading to dramatic c
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ligand was added to the [{cis-PtCl(
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spectra were measured in and refere
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4.3.1 DFT calculated Optimized Stru
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Table 4.1: A summary of the DFT cal
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H2O-Pt-L-Pt-OH2 H2O-Pt-L-Pt-OH2 H2O
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electrophilicity and acidity of the
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(A) 18 Absorbance 0.08 0.07 0.06 0.
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k obs(3 rd ) , s -1 -5 6.00x10 TMTU
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4.3.4 Kinetics with NMR The substit
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ln([ML] t ) 4.0 3.5 3.0 2.5 2.0 1.5
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ln(k 2(1 st ) /T) -3.5 -4.0 -4.5 -5
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Comple x Table 4.4: Summary of Acti
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The decrease in reactivity of 2,6pz
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Table 4.5: DFT calculated (NBO) cha
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eaction proceeds via bimolecular pa
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References 1 T. Storr, K. H.Thomson
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36 D. Jaganyi, D. Reddy, J.A. Gerte
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Appendix 4 THE INFLUENCE OF THE PYR
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Absorbance at 368. 0 nm 0. 0 8 0. 0
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Table S4.3: Average observed rate c
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k nd obs(2 ) , s-1 0.003 TU DMTU TM
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k obs2 , s -1 2.40x10 -4 2.20x10 -4
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Table S4.13: Average observed rate
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k obs(1 st ) , s -1 0.06 0.04 0.02
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ln(k 2(3 rd ) /T) -10.0 -10.5 -11.0
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SpinWorks 2.5: 2,6 pznClO4 in D2O N
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Table of Contents-5 Chapter 5 .....
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List of Tables Table 5.1: A summary
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5.1 Introduction Multinuclear plati
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onding. For this reason, pKa titrat
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400-300 cm -1): 3308, 3117, 3071 (N
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5.2.6 Spectrophotometric pKa Titrat
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Table 5.1: A summary of DFT-calcula
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However, because the highest occupi
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Table 5.2: Acid dissociation consta
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Table 5.3: A summary of DFT calcula
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H3N 6 eq TU 0 eq TU Ha NH3 Ha Cl TU
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third step due to the trans-effect
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[H 2 O-Pt-(NN)-Pt-OH 2 ] +4 [NU-Pt-
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k obs(1st) / s -1 0.20 TU DMTU TMTU
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thiourea nucleophile is large enoug
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ln(k st 2(1 ) /T) -3 -4 -5 -6 -7 -8
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is the same as the electron-withdra
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associative mode of substitution me
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16 H. Ertürk, J. Maigut, R. Puchta
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43 (a) D. Jaganyi, A. Hofmann and R
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276 nm Absorbance 0 . 6 5 0 . 6 4 0
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k obs(1 st ) , s -1 0.4 0.3 0.2 0.1
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ln(k 2(2 nd ) /T) -8.0 TU -8.5 -9.0
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pzn PPM -1750.0 -1850.0 -1950.0 -20
Page 264 and 265: Table S5.9: Average observed rate c
Page 266 and 267: Figure S5.13: UV/Visible spectra fo
Page 268 and 269: k obs(1 st ) in s -1 0.030 0.025 0.
Page 270 and 271: Table S5.17: Average observed rate
Page 272 and 273: ln(k 2(2 nd ) /T) -10 -11 -12 -13 -
Page 274 and 275: 9.61 ppm Ha PPM 9.8 9.6 9.4 9.2 9.0
Page 278 and 279: k obs(3rd) / s -1 -5 8 .00 x 10 T U
Page 280 and 281: ln(k st 2(1 ) /T) -1.5 TU DMTU TMTU
Page 282 and 283: ln(k rd 2(3 ) /T) -8.5 -9.0 -9.5 -1
Page 284 and 285: SpinWorks 2.5: znPt(II)-OP4 in D2O
Page 286 and 287: Figure S5.31: Mass spectrum for com
Page 292 and 293: ln(k st 2(1 ) /T) -4 -5 -6 -7 -8 -9
Page 294 and 295: SpinWorks 2.5: phtPt(II)-OP2 in D2O
Page 296 and 297: Figure S5.41: Mass spectrum for com
Page 298 and 299: List of Figures Figure 6.1: Spectro
Page 300 and 301: Chapter 6 Tuning Reactivity of Plat
Page 302 and 303: Against this background, several re
Page 304 and 305: 6.2.2 Instruments Microanalyses wer
Page 306 and 307: Metal Complex Pt3 Yield: 52.5 mg (0
Page 308 and 309: 6.3 Results 6.3.1 Synthesis and Cha
Page 310 and 311: The pKa values obtained are summari
Page 312 and 313: Table 6.2: DFT-calculated parameter
Page 316 and 317: It can be concluded that substituti
Page 318 and 319: ate constants, kobs(1 st /2 nd ), w
Page 320 and 321: Table 6.3: Summary of rate constant
Page 322 and 323: 6.3.6 Activation Parameters The act
Page 324 and 325: pKa1 values become smaller. In addi
Page 326 and 327: of steric influence is felt by the
Page 328 and 329: 6.5 Conclusion The present study ha
Page 330 and 331: 17 O. F. Wendt and L. I. Elding, 19
Page 332 and 333: 51 Y. Iwadata, K. Kawamura, K. Igar
Page 336 and 337: Table S6.4(b): Average observed rat
Page 338 and 339: ln(k 2(2 nd ) /T) -4 -6 -8 -10 -12
Page 340 and 341: 45.0 40 35 30 25 20 %T 15 10 5 0 -5
Page 342 and 343: k st obs(1 ) in s-1 0.30 Br TU 0.25
Page 346 and 347: -2304.16 ppm H 3N PPM -2200.0 -2220
Page 352 and 353: Absorbance 1.6 1.4 1.2 1.0 0.8 0.6
Page 354 and 355: SH N SH + Mechanism Br N + CO 3 2-
Page 356 and 357: Figure 7.5: 195Pt NMR spectra of mi
Page 358 and 359: linker remained coordinated to the
Page 360 and 361: complexes, have a lower charge and
Page 362 and 363: ange 326-400 cm -1 (weak) for Pt-Cl
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ButPt, HexPt, OctPt and DecPt, were
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7.3 Results 7.3.1 DFT Calculations
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Structure HOMO LUMO EnPt (C2h) Prop
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Absorbance Table 7.2: Summary of pK
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coordination to the soft Pt(II) cen
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observed at -2962.4 and -3024.1 ppm
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H 3N NH 3 Pt NH 2 OH 2 n NH 3 NH 2
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k obs2 , in s -1 -3 TU 1.2x10 DMTU
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7.3.4 Activation Parameters The tem
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density is located on the metal cen
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acetylmethionine, which reported th
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References 1 (a) B. Rosenberg, L. V
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32 N. Summa, J. Maigut, R. Puchta a
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Appendix 7 Table S7.1: Summary of s
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k obs(2 nd ) , in s -1 0.00020 0.00
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ln(k 2(2 nd ) /T) -8.5 -9.0 -9.5 -1
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k obs(1 st ) , in s -1 0.06 TU DMTU
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ln(k 2(1 st ) /T) -3.2 TU DMTU TMTU
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Table S7.11: Summary of kobs(2 nd )
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%T 22.0 20 18 16 14 12 10 8 6 4 2 0
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k st obs(1 ) , in s-1 0.10 0.08 0.0
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ln(k st 2(1 ) /T) -4.0 TU DMTU TMTU
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Figure S7.23: Mass spectra for HexP
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Table S21: Average observed rate co
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Table S7.23: Summary of kobs(2 nd )
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90.0 80 70 60 50 40 30 20 %T 10 0 -
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Figure S7.37: Mass spectrum for Hex
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Chapter 8 Tuning Reactivity of plat
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dinuclear Pt(II) complexes to relea
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finally Pt2. The order of reactivit
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• prolonged survival in the cell
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Tuning Reactivity of Platinum(II) Complexes

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