Rational Design of 7-Azaindole-Based Robust Microporous Hydrogen-Bonded Organic Framework for Gas Sorption.

7-Azaindole has been integrated as building block with complementary N-H⋅⋅⋅N hydrogen bonding sites for the synthesis of a tetrahedral molecular tecton, namely tetra(α-carbolin-6-yl)methane, TACM. The self-assembly of this molecule results in a 3D hydrogen-bonded organic framework (HOF). This supramolecular structure constitutes a crystalline microporous material with an extraordinary thermal and chemical robustness. Single crystal X-ray diffraction reveals how the five-fold catenation of diamonoid systems, stabilized by hydrogen bonds and π-π interactions, form an interpenetrated network with monodimensional channels. The structural features of the crystalline material are also observed by transmission electron microscopy (TEM). Additionally, the microporosity of the activated TACM-HOF is characterized by gas sorption (N2, CO2, CH4 and H2) experiments performed at different pressures. A selective adsorption is observed for CO2 uptake and TACM-HOF also presents a good adsorption capacity for H2 among supramolecular organic frameworks.

Photoactivatable Ruthenium Complexes Containing Minimal Straining Benzothiazolyl-1,2,3-triazole Chelators for Cancer Treatment.

Ruthenium(II) complexes containing diimine ligands have contributed to the development of agents for photoactivated chemotherapy. Several approaches have been used to obtain photolabile Ru(II) complexes. The two most explored have been the use of monodentate ligands and the incorporation of steric effects between the bidentate ligands and the Ru(II). However, the introduction of electronic effects in the ligands has been less explored. Herein, we report a systematic experimental, theoretical, and photocytotoxicity study of a novel series of Ru(II) complexes Ru1-Ru5 of general formula [Ru(phen)2(N∧N')]2+, where N∧N' are different minimal strained ligands based on the 1-aryl-4-benzothiazolyl-1,2,3-triazole (BTAT) scaffold, being CH3 (Ru1), F (Ru2), CF3 (Ru3), NO2 (Ru4), and N(CH3)2 (Ru5) substituents in the R4 of the phenyl ring. The complexes are stable in solution in the dark, but upon irradiation in water with blue light (λex = 465 nm, 4 mW/cm2) photoejection of the ligand BTAT was observed by HPLC-MS spectrometry and UV-vis spectroscopy, with t1/2 ranging from 4.5 to 14.15 min depending of the electronic properties of the corresponding BTAT, being Ru4 the less photolabile (the one containing the more electron withdrawing substituent, NO2). The properties of the ground state singlet and excited state triplet of Ru1-Ru5 have been explored using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. A mechanism for the photoejection of the BTAT ligand from the Ru complexes, in H2O, is proposed. Phototoxicity studies in A375 and HeLa human cancer cell lines showed that the new Ru BTAT complexes were strongly phototoxic. An enhancement of the emission intensity of HeLa cells treated with Ru5 was observed in response to increasing doses of light due to the photoejection of the BTAT ligand. These studies suggest that BTAT could serve as a photocleavable protecting group for the cytotoxic bis-aqua ruthenium warhead [Ru(phen)2(OH2)2]2+.

Novel 2-(5-Arylthiophen-2-yl)-benzoazole Cyclometalated Iridium(III) dppz Complexes Exhibit Selective Phototoxicity in Cancer Cells by Lysosomal Damage and Oncosis.

A second-generation series of biscyclometalated 2-(5-aryl-thienyl)-benzimidazole and -benzothiazole Ir(III) dppz complexes [Ir(C^N)2(dppz)]+, Ir1-Ir4, were rationally designed and synthesized, where the aryl group attached to the thienyl ring was p-CF3C6H4 or p-Me2NC6H4. These new Ir(III) complexes were assessed as photosensitizers to explore the structure-activity correlations for their potential use in biocompatible anticancer photodynamic therapy. When irradiated with blue light, the complexes exhibited high selective potency across several cancer cell lines predisposed to photodynamic therapy; the benzothiazole derivatives (Ir1 and Ir2) were the best performers, Ir2 being also activatable with green or red light. Notably, when irradiated, the complexes induced leakage of lysosomal content into the cytoplasm of HeLa cancer cells and induced oncosis-like cell death. The capability of the new Ir complexes to photoinduce cell death in 3D HeLa spheroids has also been demonstrated. The investigated Ir complexes can also catalytically photo-oxidate NADH and photogenerate 1O2 and/or •OH in cell-free media.

Cyclometalated Benzimidazole Osmium(II) Complexes with Antiproliferative Activity in Cancer Cells Disrupt Calcium Homeostasis.

We present the synthesis and characterization of six new heteroleptic osmium(II) complexes of the type [Os(C^N)(N^N)2]OTf (N^N = 2,2'-bipyridine and dipyrido[3,2-d:2',3'-f]quinoxaline; C^N = deprotonated methyl 1-butyl-2aryl-benzimidazolecarboxylate) with varying substituents in the R3 position of the phenyl ring of the cyclometalating C^N ligand. The new compounds are highly kinetically inert and absorb a full-wavelength range of visible light. An investigation of the antiproliferative activity of the new compounds has been performed using a panel of human cancer and noncancerous 2D cell monolayer cultures under dark conditions and green light irradiation. The results demonstrate that the new Os(II) complexes are markedly more potent than conventional cisplatin. The promising antiproliferative activity of selected Os(II) complexes was also confirmed using 3D multicellular tumor spheroids, which have the characteristics of solid tumors and can mimic the tumor tissue microenvironment. The mechanism of antiproliferative action of complexes has also been investigated and revealed that the investigated Os(II) complexes activate the endoplasmic reticulum stress pathway in cancer cells and disrupt calcium homeostasis.

Ru(ii) photosensitizers competent for hypoxic cancers via green light activation.

A family of five heteroleptic complexes [Ru(C^N)(N^N)2][PF6] (HC^N = methyl 1-butyl-2-arylbenzimidazolecarboxylate; N^N = polypyridine) has been synthesized to act as biologically-compatible green light photosensitizers (PSs) with phototherapeutic indexes (PIs) up to higher than 700 under hypoxia (2% O2) in HeLa cancer cells under short time of irradiation.

Luminescent Gold(I) Complexes of 1-Pyridyl-3-anthracenylchalcone Inducing Apoptosis in Colon Carcinoma Cells and Antivascular Effects.

The luminescent chalcone gold(I) conjugates [Au(PPh3)(AN3E)]PF6(1) and [Au(SIMes)(AN3E)]PF6 (2) (AN3E = (E)-3-(9-anthracenyl)-1-(4-pyridyl)propenone; SIMes = N,N'-dimesitylimidazolidin-2-ylidene; Mes = 2,4,6-trimethylphenyl)) were prepared and characterized; complex 1 was also characterized by X-ray crystallography. In MTT assays against a panel of three human colon, a melanoma and a breast cancer cell lines both complexes were antiproliferative with low micromolar IC50 values. It is noteworthy that HCT116p53-/- colon carcinoma cells lacking functional p53 (a vital tumor suppressor) were more susceptible to them than the wildtype parent cell line. In flow cytometry analyses, the gold conjugates induced a significant arrest in G2/M phase primarily. Complexes 1 and 2 quickly increased the production of reactive oxygen species (ROS) and induced mitochondrial membrane potential depolarization, higher ROS values being obtained after coadministration with enzymatic inhibitors. The free chalcone AN3E and its gold(I) complex conjugates located in the cell mitochondria according to confocal microscopy. In addition, complexes 1 and 2 showed in vivo antivascular effects on the chorioallantoic membrane (CAM) of fertilized specific-pathogen-free (SPF) chicken eggs.

New half-sandwich ruthenium(ii) complexes as proteosynthesis inhibitors in cancer cells.

Half-sandwich ruthenium(ii) complexes [(η6-p-cymene)Ru(C^N)-(X)]0/+ (X = Cl, py or 4-NMe2-py) containing a cyclometalated 2-ppy or 1-ppz with a non-coordinated CHO group as a handle for further functionalization have been synthesized to achieve selective cytotoxicity to cancer cells, the more potent compounds acting as proteosynthesis inhibitors; this is a new mode of action for half-sandwich metal complexes.

Organoruthenium Complexes with C

Our study demonstrates that four novel kinetically inert C,N-cyclometalated RuII complexes of the type [Ru(C^N)(N^N)2 ][PF6 ] containing a handle for functionalization on the C^N ligand are very potent cytotoxic agents against several different human cancer cell lines and are up to 400-fold more potent than clinically used cisplatin. In addition, the investigated ruthenium complexes are less cytotoxic in noncancerous cells, and exhibit higher selectivity for cancer cells than conventional platinum anticancer drugs. The high potency of the investigated ruthenium compounds can be attributed to several factors, including enhanced internalization and their capability to change mitochondrial transmembrane potential in cells. The new ruthenium complexes also interfere with protein synthesis with a markedly higher potency than conventional inhibitors of DNA translation. Notably, the latter mechanism has not been hitherto described for other cytotoxic Ru compounds and cisplatin.

DFT Simulation of Structural and Optical Properties of 9-Aminoacridine Half-Sandwich Ru(II), Rh(III), and Ir(III) Antitumoral Complexes and Their Interaction with DNA.

In this work, we use DFT-based methods to simulate the chemical structures, optical properties, and interaction with DNA of a recently synthesized chelated C^N 9-aminoacridine arene Ru(II) anticancer agent and two new closely related Rh(III) and Ir(III) complexes using DFT-based methods. Four chemical models and a number of theoretical approaches, which representatively include the PBE0, B97D, ωB97X, ωB97X-D, M06, and M06-L density functionals and the LANL2DZ, def2-SVP, and def2-TZVP basis sets, are tested. The best overall accuracy/cost performance for the optimization process is reached at the ωB97X-D/def2-SVP and M06/def2-SVP levels of theory. Inclusion of explicit solvent molecules (CHCl3) further refines the geometry, while taking into account the crystal network gives no significant improvements of the computed bond distances and angles. The analysis of the excited states reveals that the M06 level matches better the experimental absorption spectra, compared to ωB97X-D. The use of the M06/def2-SVP approach is therefore a well-balanced method to study theoretically the bioactivity of this type of antitumoral complexes, so we couple this TD-DFT approach to molecular dynamics simulations in order to assess their reactivity with DNA. The reported results demonstrate that these drugs could be used to inject electrons into DNA, which might broaden their applications in photoactivated chemotherapy and as new materials for DNA-based electrochemical nanodevices.

New Acridine Thiourea Gold(I) Anticancer Agents: Targeting the Nucleus and Inhibiting Vasculogenic Mimicry.

Two new 1-acridin-9-yl-3-methylthiourea Au(I) DNA intercalators [Au(ACRTU)2]Cl (2) and [Au(ACRTU) (PPh3)]PF6 (3) have been prepared. Both complexes were highly active in the human ovarian carcinoma cisplatin-sensitive A2780 cell line, exhibiting IC50 values in the submicromolar range. Compounds 2 and 3 are also cytotoxic toward different phenotypes of breast cancer cell lines MDA-MB-231 (triple negative), SK-BR-3 (HER2+, ERα-, and ERß-), and MCF-7 (ER+). Both complexes induce apoptosis through activation of caspase-3 in vitro. While inhibition of some proteins (thiol-containing enzymes) seems to be the main mechanism of action for cytotoxic gold complexes, 2 and 3 present a DNA-dependent mechanism of action. They locate in the cell nucleus according to confocal microscopy and transmission electronic microscopy. The binding to DNA resulted to be via intercalation as shown by spectroscopic methods and viscometry, exhibiting a dose-dependent response on topoisomerase I mediated DNA unwinding. In addition, 2 and 3 exhibit potent antiangiogenic effects and are also able to inhibit vasculogenic mimicry of highly invasive MDA-MB-231 cells.

First synthesis and biological evaluation of 4-amino-2-aryl-6,9-dichlorobenzo[g]pteridines as inhibitors of TNF-α and IL-6.

A direct new synthetic method on the chemistry of benzo[g]pteridines is reported. Reactions between 5,8-dichloro-2,3-dicyanoquinoxaline and benzamidines gave 4-amino-2-aryl-6,9-dichlorobenzo[g]pteridines in high to quantitative yields. The molecular structure of an N-acetyl derivative of a member of this family of compounds, 4-acetamido-6,9-dichloro-2-phenylbenzo[g]pteridine, was determined by X-ray crystallography. The synthesized compounds were evaluated for their potential anti-inflammatory activity as inhibitors of the pro-inflammatory cytokines TNF-α and IL-6. Compounds 5b, 5d and 5i showed the highest level of inhibition of both cytokines. The rest of the compounds into the series (5a, 5f, 5g and 5h), with the only exceptions of compounds 5c and 5e, which were unable to inhibit TNF-α and were the two compounds with the lower effect upon IL-6, were also able to reach good levels of inhibition of TNF-α and even higher levels of inhibition of IL-6.

Novel bis-C,N-cyclometalated iridium(III) thiosemicarbazide antitumor complexes: interactions with human serum albumin and DNA, and inhibition of cathepsin B.

A series of new organoiridium(III) complexes [Ir(N-C)(2)(N-S)]Cl (HN-C = 2-phenylpyridine (Hppy), N-S = methyl thiosemicarbazide (1), phenyl thiosemicarbazide (2) and naphtyl thiosemicarbazide (3)) have been synthesized and characterized. The crystal structure of (1) has been established by X-ray diffraction, showing the thiosemicarbazide ligand bound to the iridium atom as N,S-chelate. The cytotoxicity studies show that they are more active than cisplatin (about 5-fold) in T47D (breast cancer) at 48 h incubation time. On the other hand, very low resistance factors (RF) of 1-3 in A2780cisR (cisplatin-resistant ovarian carcinoma) at 48 h were observed (RF ≈ 1). Ir accumulation in T47D cell line after 48 h continuous exposure for complexes 1-3 are higher than that corresponding to cisplatin (about 10 times). The complexes 1-3 bind strongly to HSA with binding constants of about 10(4) M(-1) at 296 K, binding occurring at the warfarin site I for 2. Complexes 2 and 3 are also capable of binding in the minor groove of DNA as shown by Hoechst 33258 displacement experiments. Furthermore, complex 2 is also a good cathepsin B inhibitor (an enzyme implicated in a number of cancer related events), being the enzyme reactivated by cysteine.

Synthesis and biological evaluation of 4-alkoxy-6,9-dichloro[1,2,4]triazolo[4,3-a]quinoxalines as inhibitors of TNF-α and IL-6.

An efficient synthetic method for previously unattainable 4-alkoxy-6,9-dichloro[1,2,4]triazolo[4,3-a]quinoxalines has been established. Reactions between 5,8-dichloro-2,3-dicyanoquinoxaline and alcohols in the presence of triethylamine led to 3-alkoxy-5,8-dichloro-2-cyanoquinoxalines in high to quantitative yields. These compounds were treated with hydrazine giving 3-alkoxy-5,8-dichloro-2-hydrazinoquinoxalines in near quantitative yields, that reacted with triethyl orthoformate to provide the title compounds in high yields. The molecular structure of a member of this family of compounds: 6,9-dichloro-4-ethoxy[1,2,4]triazolo[4,3-a]quinoxaline, was determined by X-ray crystallography. The series of compounds synthesized were evaluated for their potential anti-inflammatory activity as inhibitors of the pro-inflammatory cytokines TNF-α and IL-6. Compounds 8e, 8a, 8b and 8g presented simultaneously good levels of inhibition of both cytokines being compound 8e the most concomitantly potent one. Compounds 8d, 8f and 8h specifically inhibited IL-6 with no significant inhibition of TNF-α. Compound 8c was not significantly active upon TNF-α, and showed no activity upon IL-6.

A novel ruthenium(II) arene based intercalator with potent anticancer activity.

The new ruthenium(II) compound [(eta6-p-cymene)Ru(N insertion mark C)Cl] (HN insertion mark C=9-aminoacridine (9-HAA)) shows a potent in vitro anticancer activity.

Acetonimine and 4-imino-2-methylpentan-2-amino platinum(II) complexes: synthesis and in vitro antitumor activity.

The reaction of [Pt(dmba)(PPh3)Cl] [where dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl] with aqueous ammonia in acetone in the presence of AgClO4 gives the acetonimine complex [Pt(dmba)(PPh3)(NH=CMe2)]ClO4 (1). The reaction of [Pt(dmba)(DMSO)Cl] with aqueous ammonia in acetone in the presence of AgClO4 gives a mixture of [Pt(dmba)(NH=CMe2)2]ClO4 (2) and [Pt(dmba)(imam)]ClO4 (3a) (where imam = 4-imino-2-methylpentan-2-amino). [Pt(dmba)(DMSO)Cl] reacts with [Ag(NH=CMe2)2]ClO4 in a 1:1 molar ratio to give [Pt(dmba)(DMSO)(NH=CMe2)]ClO4 (4). The reaction of [Pt(dmba)(DMSO)Cl] with 20% aqueous ammonia in acetone at 70 degrees C in the presence of KOH gives [Pt(dmba)(CH2COMe)(NH=CMe2)] (5), whereas the reaction of [Pt(dmba)(DMSO)Cl] with 20% aqueous ammonia in acetone in the absence of KOH gives [Pt(dmba)(imam)]Cl (3b). The reaction of [NBu4]2[Pt2(C6F5)4(mu-Cl)2] with [Ag(NH=CMe2)2]ClO4 in a 1:2 molar ratio produces cis-[Pt(C6F5)2(NH=CMe2)2] (6). The crystal structures of 1 x 2 Me2CO, 2, 3a, 5, and 6 have been determined. Values of IC50 were calculated for the new platinum complexes against a panel of human tumor cell lines representative of ovarian (A2780 and A2780 cisR) and breast cancers (T47D). At 48 h incubation time complexes 1, 4, and 5 show very low resistance factors against an A2780 cell line which has acquired resistance to cisplatin. 1, 4, and 5 were more active than cisplatin in T47D (up to 30-fold in some cases). The DNA adduct formation of 1, 4, and 5 was followed by circular dichroism and electrophoretic mobility.

New palladium(II) and platinum(II) complexes with 9-aminoacridine: structures, luminiscence, theoretical calculations, and antitumor activity.

The new complexes [Pd(dmba)( N10-9AA)(PPh 3)]ClO 4 ( 1), [Pt(dmba)( N9-9AA)(PPh 3)]ClO 4 ( 2), [Pd(dmba)( N10-9AA)Cl] ( 3), and [Pd(C 6F 5)( N10-9AA)(PPh 3)Cl] ( 4) (9-AA = 9-aminoacridine; dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl) have been prepared. The crystal structures have been established by X-ray diffraction. In complex 2, an anagostic C-H...Pt interaction is observed. All complexes are luminescent in the solid state at room temperature, showing important differences between the palladium and platinum complexes. Complex 2 shows two structured emission bands at high and low energies in the solid state, and the lifetimes are in agreement with excited states of triplet parentage. Density functional theory and time-dependent density functional theory calculations for complex 2 have been done. Values of IC 50 were also calculated for the new complexes 1- 4 against the tumor cell line HL-60. All of the new complexes were more active than cisplatin (up to 30-fold in some cases). The DNA adduct formation of the new complexes synthesized was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pB R322 were also obtained.

Palladium(II) and platinum(II) organometallic complexes with 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine. Antitumor activity of the platinum compounds.

Palladium and platinum complexes with HmtpO (where HmtpO=4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine, an analogue of the natural occurring nucleobase hypoxanthine) of the types [M(dmba)(PPh3)(HmtpO)]ClO4[dmba=N,C-chelating 2-(dimethylaminomethyl)phenyl; M=Pd or Pt], [Pd(N-N)(C6F5)(HmtpO)]ClO4[N-N=2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), or N, N, N', N'-tetramethylethylenediamine (tmeda)] and cis-[M(C6F5)2(HmtpO)2] (M=Pd or Pt) (head-to-head atropisomer in the solid state) have been obtained. Pd(II) and Pt(II) complexes with the anion of HmtpO of the types [Pd(tmeda)(C6F5)(mtpO)], [Pd(dmba)(micro-mtpO)] 2, and [NBu4]2[M(C6F5)2(micro-mtpO)]2(M=Pd or Pt) have been prepared starting from the corresponding hydroxometal complexes. Complexes containing simultaneously both the neutral HmtpO ligand and the anionic mtpO of the type [NBu4][M(C6F5)2(HmtpO)(mtpO)] (M=Pd or Pt) have been also obtained. In these mtpO-HmtpO metal complexes, for the first time, prototropic exchange is observed between the two heterocyclic ligands. The crystal structures of [Pd(dmba)(PPh 3)(HmtpO)]+, cis-[Pt(C6F5)2(HmtpO)2].acetone, [Pd(C6F5)(tmeda)(mtpO)].2H2O, [Pd(dmba)(micro-mtpO)]2, [NBu4]2[Pd(C6F5)2(micro-mtpO)]2.CH2Cl2.toluene, [NBu4]2[Pt(C6F5)2(micro-mtpO)](2).0.5(toluene), and [NBu4][Pt(C6F5)2(mtpO)(HmtpO)] have been established by X-ray diffraction. Values of IC50 were calculated for the new platinum complexes cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 against a panel of human tumor cell lines representative of ovarian (A2780 and A2780 cisR), lung (NCI-H460), and breast cancers (T47D). At 48 h incubation time, both complexes were about 8-fold more active than cisplatin in T47D and show very low resistance factors against an A2780 cell line, which has acquired resistance to cisplatin. The DNA adduct formation of cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by these platinum complexes on plasmid DNA pB R322 were also obtained.

Synthesis, structure, and luminescence of di- and trinuclear palladium/gold and platinum/gold complexes with (2,7-di-tert-butylfluoren-9-ylidene)methanedithiolate.

Acetone solutions of [Au(OClO3)(PCy3)] react with complexes [M{S2C=(t-Bu-fy)}2]2- [t-Bu-fy=2,7-di-tert-butylfluoren-9-ylidene; M=Pd (2a), Pt (2b)] or [M{S2C=(t-Bu-fy)}(dbbpy)] [dbbpy=4,4'-di-tert-butyl-2,2'-bipyridyl; M=Pd (3a), Pt (3b)] to give the heteronuclear complexes [M{S2C=(t-Bu-fy)}2{Au(PCy3)}2] [2:1 molar ratio; M=Pd (4a), Pt (4b)], [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}]ClO4 [1:1 molar ratio; M=Pd (5a), Pt (5b)], or [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}2](ClO4)2 [2:1 molar ratio; M=Pd (6a), Pt (6b)]. The crystal structures of 3a, 4a, 4b, 5b, and 6a have been solved by single-crystal X-ray studies and, in the cases of the heteronuclear derivatives, reveal the formation of short Pd...Au or Pt...Au metallophilic contacts in the range of 3.048-3.311 A. Compounds 4a and b and 5a and b undergo a dynamic process in solution that involves the migration of the [Au(PCy3)]+ units between the sulfur atoms of the dithiolato ligands. The coordination of 2a and b and 3a and b to [Au(PCy3)]+ units results in important modifications of their photophysical properties. The dominant effect in the absorption spectra is an increase in the energy of the MLCT (4a and b) or charge transfer to diimine (5a, b, 6a, b) transitions because of a decrease in the energies of the mixed metal/dithiolate HOMOs. The Pd complexes 2a and 4a are luminescent at 77 K, and the features of their emissions are consistent with an essentially metal-centered 3d-d state. The Pt/Au complexes are also luminescent at 77 K, and their emissions can be assigned as originating from a MLCT triplet state (4b) or a mixture of charge transfer to diimine and diimine intraligand pi-pi* triplet states (5b and 6b).

Palladium(II) and platinum(II) organometallic complexes with the model nucleobase anions of thymine, uracil, and cytosine: antitumor activity and interactions with DNA of the platinum compounds.

Pd(II) and Pt(II) complexes with the anions of the model nucleobases 1-methylthymine (1-MethyH), 1-methyluracil (1-MeuraH), and 1-methylcytosine (1-MecytH) of the types [Pd(dmba)(mu-L)]2 [dmba = N,C-chelating 2-((dimethylamino)methyl)phenyl; L = 1-Methy, 1-Meura or 1-Mecyt] and [M(dmba)(L)(L')] [L = 1-Methy or 1-Meura; L' = PPh(3) (M = Pd or Pt), DMSO (M = Pt)] have been obtained. Palladium complexes of the types [Pd(C6F5)(N-N)(L)] [L = 1-Methy or 1-Meura; N-N = N,N,N',N'-tetramethylethylenediamine (tmeda), 2,2'-bipyridine (bpy), or 4,4'-dimethyl-2,2'-bipyridine (Me2bpy)] and [NBu4][Pd(C6F5)(1-Methy)2(H2O)] have also been prepared. The crystal structures of [Pd(dmba)(mu-1-Methy)]2, [Pd(dmba)(mu-1-Mecyt)]2.2CHCl3, [Pd(dmba)(1-Methy)(PPh3)].3CHCl3, [Pt(dmba)(1-Methy)(PPh3)], [Pd(tmeda)(C6F5)(1-Methy)], and [NBu4][Pd(C6F5)(1-Methy)2(H2O)].H2O have been established by X-ray diffraction. The DNA adduct formation of the new platinum complexes synthesized was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the platinum complexes on plasmid DNA pBR322 were also obtained. Values of IC50 were also calculated for the new platinum complexes against the tumor cell line HL-60. All the new platinum complexes were more active than cisplatin (up to 20-fold in some cases).

New palladium(II) and platinum(II) complexes with the model nucleobase 1-methylcytosine: antitumor activity and interactions with DNA.

Palladium and platinum complexes with the model nucleobase 1-methylcytosine (1-Mecyt) of the types [Pd(N-N)(C6F5)(1-Mecyt)]ClO4 [N-N = bis(3,5-dimethylpyrazol-1-yl)methane (bpzm), bis(pyrazol-1-yl)methane (bpzm), N,N,N',N'-tetramethylethylenediamine (tmeda), or 2,2'-bipyridine (bpy)] and [M(dmba)(L')(1-Mecyt)]ClO4 [dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl; L' = PPh(3) (M = Pd or Pt), DMSO (M = Pt)] have been obtained. Palladium and platinum complexes of the types cis-[M(C6F5)2(1-Mecyt)2] (M = Pd or Pt) and cis-[Pd(L')(C6F5)(1-Mecyt)2]ClO4 (L' = PPh(3) or t-BuNC) have also been prepared. The crystal structures of [Pd(bpzm)(C6F5)(1-Mecyt)]ClO4, [Pt(dmba)(DMSO)(1-Mecyt)]ClO4, cis-[Pd(C6F5)2(1-Mecyt)2], and cis-[Pd(t-BuNC)(C6F5)(1-Mecyt)2]ClO4 have been established by X-ray diffraction. There is extensive hydrogen bonding (N-H...O, C-H...F or C-H...O) in all the compounds. There are also intermolecular pi-pi interactions between pyrimidine rings of adjacent chains in [Pd(C6F5)2(1-Mecyt)2]. DNA adduct formation of the new complexes synthesized was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pBR322 were also obtained. Values of IC(50) were also calculated for the new complexes against the tumor cell line HL-60. At a short incubation time (24 h) almost all new complexes were more active than cisplatin.