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Publikation

Bulatović, M. Z.; Maksimović-Ivanić, D.; Bensing, C.; Gómez-Ruiz, S.; Steinborn, D.; Schmidt, H.; Mojić, M.; Korać, A.; Golić, I.; Pérez-Quintanilla, D.; Momčilović, M.; Mijatović, S.; Kaluđerović, G. N.; Organozinn(IV)-beladenes mesoporöses SiO2 als biokompatible Strategie bei der Krebstherapie Angew. Chem. 126, 6092-6097, (2014) DOI: 10.1002/ange.201400763

Das große therapeutische Potenzial eines Organozinn(IV)‐beladenen nanostrukturierten SiO2 (SBA‐15pSn) wird am Beispiel der Rückbildung eines durch B16‐Zellen induzierten Melanoms bei syngenen C57BL/6‐Mäusen demonstriert. Neben Apoptose als grundlegendem Mechanismus der Antitumorwirkung einer Vielzahl von Chemotherapeutika ist der entscheidende Vorteil dieses mesoporösen zinnhaltigen Materials das Auslösen der Zelldifferenzierung – ein Effekt, der weder für metallbasierte Zytostatika noch für mesoporöse Materialien alleine bisher beobachtet wurde. Dieser nichtaggressive Wirkungsmechanismus ist hochwirksam gegen Tumorzellen aber im gewählten Konzentrationsbereich nichttoxisch für normales Gewebe. JNK‐unabhängige Apoptose (JNK: Jun amino‐terminal kinase), begleitet von der Bildung des melanozytenartigen nichtproliferativen Phänotyps der überlebenden Zellen demonstriert das außergewöhnliche Potenzial von SBA‐15pSn zur Unterdrückung von Tumorwachstum ohne eine unerwünschte kompensatorische Proliferation der erkrankten Zellen als Antwort auf den Zelltod in ihrer Nachbarschaft.
Publikation

Bulatović, M. Z.; Maksimović-Ivanić, D.; Bensing, C.; Gómez-Ruiz, S.; Steinborn, D.; Schmidt, H.; Mojić, M.; Korać, A.; Golić, I.; Pérez-Quintanilla, D.; Momčilović, M.; Mijatović, S.; Kaluđerović, G. N.; Organotin(IV)-Loaded Mesoporous Silica as a Biocompatible Strategy in Cancer Treatment Angew. Chem. Int. Ed. 53, 5982-5987, (2014) DOI: 10.1002/anie.201400763

The strong therapeutic potential of an organotin(IV) compound loaded in nanostructured silica (SBA‐15pSn) is demonstrated: B16 melanoma tumor growth in syngeneic C57BL/6 mice is almost completely abolished. In contrast to apoptosis as the basic mechanism of the anticancer action of numerous chemotherapeutics, the important advantage of this SBA‐15pSn mesoporous material is the induction of cell differentiation, an effect unknown for metal‐based drugs and nanomaterials alone. This non‐aggressive mode of drug action is highly efficient against cancer cells but is in the concentration range used nontoxic for normal tissue. JNK (Jun‐amino‐terminal kinase)‐independent apoptosis accompanied by the development of the melanocyte‐like nonproliferative phenotype of survived cells indicates the extraordinary potential of SBA‐15pSn to suppress tumor growth without undesirable compensatory proliferation of malignant cells in response to neighboring cell death.
Publikation

Kluge, T.; Bette, E.; Bette, M.; Schmidt, J.; Steinborn, D.; Hydrazone–diacetyl platinum(II) complexes: Substituent effect on intramolecular N–H⋯O hydrogen-bond strength J. Organomet. Chem. 762, 48-57, (2014) DOI: 10.1016/j.jorganchem.2014.03.030

Bis(benzylamine)diacetylplatinum(II) (3) reacted with 2-pyridyl-functionalized hydrazones and with diacetyl dihydrazone to yield diacetyl platinum(II) complexes [Pt(COMe)2(2-pyCRNNH2)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(H2NNCMe–CMeNNH2)] (5). These complexes showed weak intramolecular N–H⋯O hydrogen bonds where the hydrazone and the acetyl ligand act as H donor and H acceptor, respectively. Using hydrazones 2-pyCRNNHR′ substituted with electron-withdrawing groups R′ resulted in complexes [Pt(COMe)2(2-pyCRNNHR′)] (R/R′ = H/C6H4-p-F, 6d; Me/C6H4-p-F, 6e; H/COMe, 7a; Me/COMe, 7b; H/COPh, 7c; Me/COPh, 7d; H/CO(C6H4-p-F), 7e; Me/CO(C6H4-p-F), 7f) with stronger intramolecular N–H⋯O hydrogen bonds. The isolation of the analogous phenylhydrazone complexes (R′ = Ph) failed on this way, but reactions of the 1D coordination polymer [{Pt(COMe)2}n] (2) with phenylhydrazones resulted in the formation of the desired complexes [Pt(COMe)2(2-pyCRNNHR′)] (R/R′ = H/Ph, 6a; Me/Ph, 6b; Ph/Ph, 6c; H/C6F5, 6f). The constitution of all complexes was unambiguously confirmed analytically, spectroscopically and, in part, by single-crystal X-ray diffraction analyses. Structural and NMR parameters gave evidence that the strength of the N–H⋯O hydrogen bond is increased in the order 5 ≈ 4a–c < 6a–e < 6f ≈ 7a–f. This goes parallel with an activation of the acetyl ligand, but in no case the reaction with amines resulted in the formation of iminoacetyl platinum(II) complexes as it was found in analogous oxime–diacetyl complexes [Pt(COMe)2(2-pyCRNOH)] which have stronger (even than in type 6f/7a–f complexes) intramolecular O–H⋯O hydrogen bonds.
Publikation

Chaudhuri, S. R.; Kaluđerović, G. N.; Bette, M.; Schmidt, J.; Schmidt, H.; Paschke, R.; Steinborn, D.; Synthesis, characterization and cytotoxicity studies of platinum(II) complexes with amino acid ligands in various coordination modes Inorg. Chim. Acta 394, 472-480, (2013) DOI: 10.1016/j.ica.2012.08.034

Reactions of [Pt(CO3)(PPh3)2]·CH2Cl2 (1) with non-substituted and alkyl substituted amino acids, NH(R)CH(R′)CO2H (R/R′ = H/Me, L1; H/iPr, L2; H/CH2CHMe2, L3; Me/H, L4; Et/H, L5), in the presence of Tl[PF6] in methanol afforded with liberation of CO2 the formation of platinum(II) complexes of the type [Pt(PPh3)2{NHR–CHR′–C(O)O-κN,κO}][PF6] (R/R′ = H/Me, 2; H/iPr, 3; H/CH2CHMe2, 4; Me/H, 5; Et/H, 6). Single-crystal X-ray diffraction analysis of complex 4 exhibited a square-planar coordination of the platinum atom having coordinated two triphenylphosphane ligands and a deprotonated κN,κO-coordinated leucine ligand (L3−H). On varying the pKa value of the amino group, platinum(II) complexes with different coordination modes of amino acid ligands were obtained. Thus, treatment of complex 1 with N-acetyl l-alanine (L6), possessing a comparatively highly acidic NH proton, in 1:1 ratio in methanol resulted in the formation of [Pt(PPh3)2{N(COMe)–CHMe–C(O)O-κN,κO}] (7), while reacting N-phenyl glycine (L7) having a moderately acidic NH proton with complex 1 afforded a mixture of complexes [Pt(PPh3)2{NPh–CH2–C(O)O-κN,κO}] (8) and [Pt(PPh3)2{NHPh–CH2–C(O)O-κO}2] (10). Treatment of complex 1 with two equivalents of L6/L7 in dichloromethane resulted in the formation of [Pt(PPh3)2{NHR–CHR′–C(O)O-κO}2] (R/R′ = COMe/Me, 9; Ph/H, 10). An analogous reactivity was observed for l-lactic acid on treating with complex 1 in 1:1 and 2:1 ratio resulting in [Pt(PPh3)2{O–CHMe–C(O)O-κO,κO′}] (11) and [Pt(PPh3)2{HO–CHMe–C(O)O-κO}2] (12). The identities of all complexes have been proven by NMR (1H, 13C, 31P) spectroscopic and high-resolution ESI mass-spectrometric investigations. In vitro cytotoxicity studies against human tumor cell lines (8505C, A2780, HeLa, SW480, and MCF-7) showed the highest activities for the neutral complex 7. Furthermore, complexes 7 and 9 against the A2780 cell line induced an apoptotic mode of cell death, which was further supported by morphological investigation and DNA laddering. Cell cycle perturbation studies showed that both complexes induced faster cell death than cisplatin.
Publikation

Mihály, T.; Bette, M.; Mihály, B.; Schmidt, J.; Schmidt, H.; Steinborn, D.; Synthesis, structure and characterization of adenine-based aminocarbene complexes of platinum(II) J. Organomet. Chem. 739, 57-62, (2013) DOI: 10.1016/j.jorganchem.2013.04.030

The reaction of the dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) with two equivalents of adenine and its methylated derivatives N6-R,9-R′Ade–H resulted in adenine-based aminocarbene platinum(II) complexes [Pt(COMe)Cl{CMe(N6-R,9-R′Ade–H)-κC,κN}] (R/R′ = Me/Me, 2; H/Me, 3; H/H, 4) whose identities were confirmed by NMR and IR spectroscopies as well as by high-resolution mass spectrometric investigations. Single-crystal X-ray diffraction analyses of complexes 2 and 4·THF revealed relatively short Pt–C and N–C bonds in the aminocarbene–platinum units, which is in accord with a substantial double bond character of these bonds. The electronic structure of these complexes will be further confirmed by DFT calculations as also the course of reaction.
Publikation

Bette, M.; Rüffer, T.; Bruhn, C.; Schmidt, J.; Steinborn, D.; Synthesis, Characterization, and Reactivity of Diacetylplatinum(II) and -platinum(IV) Complexes Bearing κ2- and κ3-Coordinated Scorpionate Ligands Organometallics 31, 3700-3710, (2012) DOI: 10.1021/om3001907

Reactions of the dinuclear platina-β-diketone [Pt2{(COR)2H}2(μ-Cl)2] (1) with K[(pz)3BH] and K[(3,5-Me2pz)3BH] (pz = pyrazolyl; 3,5-Me2pz = 3,5-dimethylpyrazolyl) afforded neutral diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3BH}] (4a) and [Pt(COMe)2H{(3,5-Me2pz)3BH}] (4b), bearing κ3-bonded tris(pyrazolyl)borate (scorpionate) ligands. These complexes were found to decompose in chloroform solution under formation of the respective chlorido complexes [Pt(COMe)2Cl{(pz)3BH}] (5a) and [Pt(COMe)2Cl{(3,5-Me2pz)3BH}] (5b) as the initial step. Diacetylplatinum(II) complexes with κ2-coordinated scorpionate ligands (K[Pt(COMe)2{(pz)3BH}], 6a; K[Pt(COMe)2{(3,5-Me2pz)3BH}], 6b; K[Pt(COMe)2{(pz)4B}], 7; K[{Pt(COMe)2}2{(pz)4B}], 8) were obtained in ligand exchange reactions of [Pt(COMe)2(NH2Bn)2] (3; Bn = benzyl) with the respective potassium (pyrazolyl)borates. The deprotonation of the hydrido complexes 4 with potassium methoxide led also to the formation of 6. Diacetylplatinum(II) complexes 6a and 7 were found to react in oxidative addition reactions with alkyl halides to yield diacetylplatinum(IV) complexes of the type [Pt(COMe)2R{(pz)3BH)}] (R = Me, 9a; Et, 9b; Bn, 9c) and [Pt(COMe)2R{(pz)4B}] (R = Me, 10a; Et, 10b; Bn, 10c), respectively, with κ3-bonded scorpionate ligands. The identities of all platinum complexes were unambiguously proved by microanalyses or by high-resolution mass spectrometric investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopies, and by single-crystal X-ray diffraction analyses (4a, 5a, 7·(18C6), 9c; 18C6 = 18-crown-6). The reactivity of the complexes is discussed in terms of hemilability of the scorpionate ligands.
Publikation

Kluge, T.; Bette, M.; Vetter, C.; Schmidt, J.; Steinborn, D.; Synthesis and characterization of diacetyl platinum(II) complexes with two primary and secondary amine ligands J. Organomet. Chem. 715, 93-101, (2012) DOI: 10.1016/j.jorganchem.2012.05.043

[Pt(COMe)2(bpy)] (2; bpy = 2,2′-bipyridine) and [Pt(COMe)2{H(Me)dmg}] (5; H(Me)dmg = MeO–NC(Me)–C(Me)N–OH) were found to react with primary and secondary amines yielding diacetyl platinum(II) complexes with two monodendate amine ligands [Pt(COMe)2(NH2R)2] (R = Bn, 3a; CH2CH2Ph, 3b; Et, 3c; i-Pr, 3d; CH2CHCH2, 3e; Cy, 3f; Bn = benzyl, Cy = cyclohexyl) and [Pt(COMe)2(NHR2)2] (R = Me, 6a; Et, 6b), respectively. The equilibrium of these ligand exchange reactions was investigated by NMR experiments and DFT calculations showing that complex 5 is the more preferable starting complex and a large excess of the amine has to be used. The sterically demanding diisopropylamine was found to react with 5 yielding a thermally highly unstable dinuclear bis(acetyl) bridged complex [{Pt(COMe){NH(i-Pr)2}}2(μ-COMe)2] (7). Analogous reactions with ethylenediamine derivatives resulted in the formation of [Pt(COMe)2(N^N)] (N^N = ethylenediamine, en, 8a; N,N′-dimethylethylenediamine, 8b; N,N-dimethylethylenediamine, 8c; N,N,N′,N′-tetramethylethylenediamine, TMEDA, 8d). All complexes were fully characterized by microanalysis/high-resolution ESI mass spectrometry, by NMR (1H, 13C, 195Pt) and IR spectroscopies as well as by single-crystal X-ray diffraction measurements (3a/3d). Due to the high trans influence of the acetyl ligands, the Pt–N bonds were found to be relatively long (2.164(2)–2.182(3) Å). The resulting weak coordination of the amines gave rise to a decomposition of complexes 3 under CO extrusion yielding carbonyl–methyl complexes.
Publikation

Block, M.; Bette, M.; Wagner, C.; Schmidt, J.; Steinborn, D.; Rhodium(I) complexes with κP coordinated ω-phosphinofunctionalized alkyl phenyl sulfide, sulfoxide and sulfone ligands and their reactions with sodium bis(trimethylsilyl)amide and Ag[BF4] J. Organomet. Chem. 696, 1768-1781, (2011) DOI: 10.1016/j.jorganchem.2010.12.019

Reactions of ω-diphenylphosphinofunctionalized alkyl phenyl sulfides Ph2P(CH2)nSPh (n = 1, 1a; 2, 2a; 3, 3a), sulfoxides Ph2P(CH2)nS(O)Ph (n = 1, 1b; 2, 2b; 3, 3b) and sulfones Ph2P(CH2)nS(O)2Ph (n = 1, 1c; 2, 2c; 3, 3c) with dinuclear chlorido bridged rhodium(I) complexes [(RhL2)2(μ-Cl)2] (L2 = cycloocta-1.5-diene, cod, 4; bis(diphenylphosphino)ethane, dppe, 5) afforded mononuclear Rh(I) complexes of the type [RhCl{Ph2P(CH2)nS(O)xPh-κP}(cod)]1 (n/x = 1/0, 6a; 1/1, 6b; 1/2, 6c; 2/0, 8a; 2/1, 8b; 2/2, 8c; 3/0, 10a; 3/1, 10b; 3/2, 10c) and [RhCl{Ph2P(CH2)nS(O)xPh-κP}(dppe)] (n/x = 1/0, 7a; 1/1, 7b; 1/2, 7c; 2/0, 9a; 2/1, 9b; 2/2, 9c; 3/0, 11a; 3/1, 11b; 3/2, 11c) having the P^S(O)x ligands κP coordinated. Addition of Ag[BF4] to complexes 6–11 in CH2Cl2 led with precipitation of AgCl to cationic rhodium complexes of the type [Rh{Ph2P(CH2)nS(O)xPh-κP,κS/O}L2][BF4] having bound the P^S(O)x ligands bidentately in a κP,κS (13a–18a, 15b–18b) or a κP,κO (13b, 14b, 13c–18c) coordination mode. Unexpectedly, the addition of Ag[BF4] to 6a in THF afforded the trinuclear cationic rhodium(I) complex [Rh3(μ-Cl)(μ-Ph2PCH2SPh-κP:κS)4][BF4]2·4THF (12·4THF) with a four-membered Rh3Cl ring as basic framework. Addition of sodium bis(trimethylsilyl)amide to complexes 6–11 led to a selective deprotonation of the carbon atom neighbored to the S(O)x group (α-C) yielding three different types of organorhodium complexes: a) Organorhodium intramolecular coordination compounds of the type [Rh{CH{S(O)xPh}CH2CH2PPh2-κC,κP}L2] (22a–c, 23a–c), b) zwitterionic complexes [Rh{Ph2PCHS(O)xPh-κP,κS/O}L2] having κP,κS (21a, 21b) and κP,κO (20b/c, 21c) coordinated anionic [Ph2PCHS(O)xPh] ligands, and c) the dinuclear rhodium(I) complex [{Rh{μ-CH(SPh)PPh2-κC:κP}(cod)}2] (19). All complexes were fully characterized spectroscopically and complexes 15b, 15c, 12·4THF and 19·THF additionally by X-ray diffraction analysis. DFT calculations of zwitterionic complexes gave insight into the coordination mode of the [Ph2PCHS(O)Ph] ligand (κP,κS versus κP,κO).
Publikation

Vetter, C.; Pornsuriyasak, P.; Schmidt, J.; Rath, N. P.; Rüffer, T.; Demchenko, A. V.; Steinborn, D.; Synthesis, characterization and reactivity of carbohydrate platinum(IV) complexes with thioglycoside ligands Dalton Trans. 39, 6327-6338, (2010) DOI: 10.1039/B927058B

Reactions of fac-[PtMe3(4,4′-R2bpy)(Me2CO)][BF4] (R = H, 1a; tBu, 1b) and fac-[PtMe3(OAc-κ2O,O′)(Me2CO)] (2), respectively, with thioglycosides containing thioethyl (ch-SEt) and thioimidate (ch-STaz, Taz = thiazoline-2-yl) anomeric groups led to the formation of the carbohydrate platinum(IV) complexes fac-[PtMe3(4,4′-R2bpy)(ch*)][BF4] (ch* = ch-SEt, 8–14; ch-STaz, 15–23) and fac-[PtMe3(OAc-κ2O,O′)(ch*)] (ch* = ch-SEt, 24–28; ch-STaz = 29–35), respectively. NMR (1H, 13C, 195Pt) spectroscopic investigations and a single-crystal X-ray diffraction analysis of 19 (ch-STaz = 2-thiazolinyl 2,3,4,6-tetra-O-benzoyl-1-thio-β-D-galactopyranose) revealed the S coordination of the ch-SEt glycosides and the N coordination of the ch-STaz glycosides. Furthermore, X-ray structure analyses of the two decomposition products fac-[PtMe3(bpy)(STazH-κS)][BF4] (21a) and 1,6-anhydro-2,3,4-tri-O-benzoyl-β-D-glucopyranose (23a), where a cleavage of the anomeric C–S bond had occurred in both cases, gave rise to the assumption that this decomposition was mediated due to coordination of the thioglycosides to the high electrophilic platinum(IV) atom, in non-strictly dried solutions. Reactions of fac-[PtMe3(Me2CO)3][BF4] (3) with ch-SEt as well as with ch-SPT and ch-Sbpy thioglycosides (PT = 4-(pyridine-2-yl)-thiazole-2-yl; bpy = 2,2′-bipyridine-6-yl), having N,S and N,N heteroaryl anomeric groups, respectively, led to the formation of platinum(IV) complexes of the type fac-[PtMe3(ch*)][BF4] (ch* = ch-SEt, 36–40, ch-SPT 42–44, ch-Sbpy45, 46). The thioglycosides were found to be coordinated in a tridentate κS,κ2O,O′, κS,κN,κO and κS,κ2N,N′ coordination mode, respectively. Analogous reactions with ch-STaz ligands succeeded for 2-thiazolinyl 2,3,4-tri-O-benzyl-6-O-(2,2′-bipyridine-6-yl)-1-thio-β-D-glucopyranoside (5h) resulting in fac-[PtMe3(ch-STaz)][BF4] (41, ch-STaz = 5h), having a κ3N,N′,N′′coordinated thioglycoside ligand.
Publikation

Vetter, C.; Kaluđerović, G. N.; Paschke, R.; Kluge, R.; Schmidt, J.; Steinborn, D.; Synthesis, characterization and in vitro cytotoxicity studies of platinum(IV) complexes with thiouracil ligands Inorg. Chim. Acta 363, 2452-2460, (2010) DOI: 10.1016/j.ica.2010.03.079

Reactions of [PtMe3(bpy)(Me2CO)][BF4] (2) with the thionucleobases 2-thiouracil (s2Ura), 4-thiouracil (s4Ura) and 2,4-dithiouracil (s2s4Ura) resulted in the formation of complexes of the type [PtMe3(bpy)(L-κS)][BF4] (L = s2Ura, 3; s4Ura, 4; s2s4Ura, 5). The complexes were characterized by NMR spectroscopy (1H, 13C, 195Pt), IR spectroscopy as well as microanalyses. The coordination through the C4S groups (4, 5) was additionally confirmed by DFT calculations, where it was shown that these complexes [PtMe3(bpy)(L-κS4)]+ (L = s4Ura, s2s4Ura) are about 5.8 (4b) and 3.3 kcal/mol (5b), respectively, more stable than the respective complexes, having thiouracil ligands bound through the C2X groups (X = O, 4a; S, 5a). For [PtMe3(bpy)(s2Ura-κS2)][BF4] (3) no preferred coordination mode could be assigned solely based on DFT calculations. Analysis of NMR spectra showed the κS2 coordination. In vitro cytotoxic studies of complexes 3−5 on nine different cell lines (8505C, A253, FaDu, A431, A549, A2780, DLD-1, HCT-8, HT-29) revealed in most cases moderate activities. However, 3 and 5 showed significant activity towards A549 and A2780, respectively, possessing IC50 values comparable to those of cisplatin. Cell cycle perturbations and trypan blue exclusion test on cancer cell line A431 using [PtMe3(bpy)(s2s4Ura-κS4)][BF4] (5) showed induction of apoptotic cell death. Furthermore, the reaction of [PtMe3(OAc-κ2O,O′)(Me2CO)] (6) with 4-thiouracil yielded the dinuclear complex [(PtMe3)2(μ-s4Ura–H)2] (7), which has been characterized by microanalysis, NMR (1H, 13C, 195Pt) and IR spectroscopy as well as ESI mass spectrometry. X-ray diffraction analysis of crystals yielded in an isolated case exhibited the presence of a hexanuclear thiouracilato platinum(IV) complex, possessing each three different kinds of methyl platinum(IV) moieties and 4-thiouracilato ligands. This exhibited the ability of 4-thiouracil platinum(IV) complexes to form multinuclear complexes.
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