Nanodiamonds (NDs) have emerged as a very useful material for drug-carrier applications in nanome... more Nanodiamonds (NDs) have emerged as a very useful material for drug-carrier applications in nanomedicine. Herein, we prepared cisplatin-like structures on the surface of the NDs to investigate their potential use as anticancer drugs. Cis-diamminediiodoplatinum(II)-modified NDs have been prepared by the coordination of [PtI4]2− to amine-modified NDs. Subsequent halogen exchange of the iodine ligands with chloride ions resulted in the formation of cis-diamminedichloroplatinum(II)-modified NDs, 100% exchange occurred as detected by XPS analysis. Another cisplatin-like ND derivative has been constructed, where the platinum is anchored onto the NDs via an amine-capped silane linker. This was achieved by grafting (3-aminopropyl)trimethoxysilane (APTMES) onto the NDs, followed by coordination of the [PtI4]2− Pt-precursor and halogen exchange with Cl− to produce cis-diamminedichlorodoplatinum(II)-silane-modified NDs. Since the Pt is three methylene groups away from the ND support, it is more flexible to move and participate in reactions than the platinum of the cis-diamminedichloroplatinum(II)-modified NDs, which results in its improved IC50 value of 2.6 µml against HeLa cancer cells vs. the 6.5 µml of diamminedichloroplatinum(II)-modified NDs.
Abstract The electrochemical analysis, theoretical examination, as well as the first X-ray photoe... more Abstract The electrochemical analysis, theoretical examination, as well as the first X-ray photoelectron spectroscopic (XPS) study on molybdenum(0) Fischer carbene complexes are presented. The intramolecular communication between the carbene ligand, molybdenum metal centre, and the ancillary ligands is illustrated by linear relationships and trends obtained between experimentally measured redox and XPS binding energy values and theoretically calculated energies and charges. The ease of oxidation of the three series of Mo(0) Fischer carbene complexes presented, namely four pentacarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 5 MoC(OEt)(Ar)], with Ar = 2-thienyl ( 1 ), 2-furyl ( 2 ), 2-(N-methyl)pyrrolyl ( 3 ), 2,2'-bithienyl ( 4 ), four triphenylphosphine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 5 ), 2-furyl ( 6 ), 2-(N-methyl)pyrrolyl ( 7 ), 2,2'-bithienyl ( 8 ), and four triphenylarsine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 9 ), 2-furyl ( 10 ), 2-(N-methyl)pyrrolyl ( 11 ), 2,2'-bithienyl ( 12 ), all showed the same trend, namely (most difficult to oxidize at a higher potential): 2-thienyl ≈ 2,2'-bithienyl > 2-furyl > 2-(N-methyl)pyrrolyl. The pentacarbonyl complexes [(CO) 5 MoC(OEt)(Ar)] have the highest oxidation potentials, followed by the oxidation potential of [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], while [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)] oxidized at a potential 0.12 − 0.15 V lower than the PPh 3 substituted complexes [(CO) 4 (PPh 3 )MoC(OEt)(Ar)]. Substitution of carbonyl ligand(s) in the pentacarbonyl complexes 1 – 4 , by one (complexes 5 – 12 ) or two ([(dppe)(CO) 3 MoC(OEt)(2-furyl)] complex ( 13 ), dppe = 1,2-bis(diphenylphosphino)ethane) weaker π-acceptor ligands (phosphines/arsines) in Fischer carbene complexes leads to a decrease in the binding energy of the Mo 3d 5/2 photoelectron lines of the X-ray photoelectron spectra of the Fischer carbene complexes and an increase in the binding energy of the carbene carbon C 1 s photoelectron lines.
ABSTRACT The synthesis of a variety of tetrahedral β-diketonato titanium(IV) complexes of the typ... more ABSTRACT The synthesis of a variety of tetrahedral β-diketonato titanium(IV) complexes of the type [(C5H5)2Ti(CH3COCHCOR)]+ClO4- with R=CF3, OCH3, C6H5, CH3 and Fc is described. The TiIII/TiIV couples and the Fc/Fc+ couple exhibited chemically and electrochemically reversible cyclic voltammetric behaviour. The formal reduction potential of the TiIII/IV couple increased as the group electronegativity of the R group of the β-diketonato ligand increased. Bulk electrolysis showed that one electron was transferred in the TiIII/IV couple and one electron in the ferrocenyl/ferrocenium redox couple in the ligand. The crystal structure for the R=OCH3 complex showed that this β-keto-ester binds through the carbonyl oxygen of the ester group and not the ether oxygen.
Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diket... more Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diketonato) cobalt(III) complexes is more stable ( mer isomers are more stable because they are less affected by steric hindrance and they have lower dipoles). An excess of the mer isomer or only the mer isomer is experimentally observed. The existence of both fac and mer isomers is predicted by density functional theory calculations. At room temperature, the nuclear magnetic resonance peaks of phenyl-containing mer complexes are broad due to the intermediate rotation of bulky phenyl groups resulting in only the average orientation of the non-equivalent protons in the mer complexes. However, upon heating to 55 °C (thus speeding up the rotation) or cooling to −50 °C (slowing down the rotation), this broad peak is resolved into three sets of carbon peaks appearing in the 13C NMR spectrum, as well as splitting of the 1H NMR peaks for the non-equivalent protons in the mer isomer. In solid-state 1...
Abstract Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH2-CO-R were sy... more Abstract Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH2-CO-R were synthesised to obtain two β-diketones with R = CH3, 3, and R = Fc (ferrocenyl = FeII(C5H5)(C5H4)), 4, a β-ketoester, 5, with R = OEt and a β-ketoamide, 6, with R = NH2. The β-diketones exhibited keto ⇌ enol tautomerization with the enol form Fc-CO-CH=C(OH)-R as the dominant isomer. Both the β-ketoester and β-ketoamide primarily existed in the keto form. FTIR and 1H NMR measurements could distinguish between keto and enol isomers. Dilute CHCl3 solutions of 3 and 4 exhibited FTIR ѵC=O keto vibrations between 1627 and 1712 cm−1 and ѵC=O enol vibrations between 1590 and 1660 cm−1. X-ray photoelectron spectroscopic (XPS) measurements showed keto isomer Fe 2p3/2 photoelectron lines at smaller binding energies than enol isomers. Significantly lower calculated molecular energies of the keto form of the β-ketoester 5 and β-ketoamide 6 utilising the Gaussian09 suite of programs at the B3LYP (uB3LYP for open-shell species), confirmed that 5 and 6 almost exclusively exists in the keto conformation. Cyclic voltammetry also distinguished between keto and enol isomers, and it was found that the electrochemical reversible ferrocenyl formal oxidation potential, E°ꞌ, of keto isomers of compounds can be estimated with the equation E°ꞌketo = 170.99χR–57.57 where χR is the group electronegativities of R in FcCOCH2COR. This result complements earlier research that enables calculation of the ferrocenyl formal oxidation potentials of enol isomers of β-diketones. Computational studies further showed that the HOMO orbitals of 3–6 is exclusively on the Fe centre and computed Mulliken spin densities on the dxy orbital of the oxidised iron species approached 1 e−.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Langmuir : the ACS journal of surfaces and colloids, 2012
The bimetallic paddlewheel catalyst precursor, [Pd(II)Co(II)(μ-OOCCH(3))(4)] H(2)O·2CH(3)COOH (1)... more The bimetallic paddlewheel catalyst precursor, [Pd(II)Co(II)(μ-OOCCH(3))(4)] H(2)O·2CH(3)COOH (1), prepared from [Pd(3)(μ-OOCCH(3))(6)] and [Co(OOCCH(3))(2)], was used as a single source precursor to prepare, after binding to a surface-hydroxylated silicon wafer and oxidation, the bimetallic oxides of Pd(IV)Co(III)/SiO(2) catalyst supported on a model planar (i.e., two-dimensional) silicon wafer. This catalyst catalyzes the aerobic oxidation of alcohols to its corresponding carbonyl compounds. The bimetallic tetracarboxylato catalyst precursor was bonded to the surface-hydroxylated silicon wafer by spin-coating and also by grafting. X-ray photoelectron spectroscopy (XPS) revealed that one of the four μ-acetato bridging ligands was substituted by Si-O fragments in a covalent bond formation process during grafting of 1 onto the wafer. In contrast, during the spin-coating process, all four acetato ligands remained intact during fixation on the silicon surface. Upon oxidation and workup...
Nanodiamonds (NDs) have emerged as a very useful material for drug-carrier applications in nanome... more Nanodiamonds (NDs) have emerged as a very useful material for drug-carrier applications in nanomedicine. Herein, we prepared cisplatin-like structures on the surface of the NDs to investigate their potential use as anticancer drugs. Cis-diamminediiodoplatinum(II)-modified NDs have been prepared by the coordination of [PtI4]2− to amine-modified NDs. Subsequent halogen exchange of the iodine ligands with chloride ions resulted in the formation of cis-diamminedichloroplatinum(II)-modified NDs, 100% exchange occurred as detected by XPS analysis. Another cisplatin-like ND derivative has been constructed, where the platinum is anchored onto the NDs via an amine-capped silane linker. This was achieved by grafting (3-aminopropyl)trimethoxysilane (APTMES) onto the NDs, followed by coordination of the [PtI4]2− Pt-precursor and halogen exchange with Cl− to produce cis-diamminedichlorodoplatinum(II)-silane-modified NDs. Since the Pt is three methylene groups away from the ND support, it is more flexible to move and participate in reactions than the platinum of the cis-diamminedichloroplatinum(II)-modified NDs, which results in its improved IC50 value of 2.6 µml against HeLa cancer cells vs. the 6.5 µml of diamminedichloroplatinum(II)-modified NDs.
Abstract The electrochemical analysis, theoretical examination, as well as the first X-ray photoe... more Abstract The electrochemical analysis, theoretical examination, as well as the first X-ray photoelectron spectroscopic (XPS) study on molybdenum(0) Fischer carbene complexes are presented. The intramolecular communication between the carbene ligand, molybdenum metal centre, and the ancillary ligands is illustrated by linear relationships and trends obtained between experimentally measured redox and XPS binding energy values and theoretically calculated energies and charges. The ease of oxidation of the three series of Mo(0) Fischer carbene complexes presented, namely four pentacarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 5 MoC(OEt)(Ar)], with Ar = 2-thienyl ( 1 ), 2-furyl ( 2 ), 2-(N-methyl)pyrrolyl ( 3 ), 2,2'-bithienyl ( 4 ), four triphenylphosphine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 5 ), 2-furyl ( 6 ), 2-(N-methyl)pyrrolyl ( 7 ), 2,2'-bithienyl ( 8 ), and four triphenylarsine-substituted tetracarbonyl Mo(0) Fischer carbene complexes of general formula [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)], with Ar = 2-thienyl ( 9 ), 2-furyl ( 10 ), 2-(N-methyl)pyrrolyl ( 11 ), 2,2'-bithienyl ( 12 ), all showed the same trend, namely (most difficult to oxidize at a higher potential): 2-thienyl ≈ 2,2'-bithienyl > 2-furyl > 2-(N-methyl)pyrrolyl. The pentacarbonyl complexes [(CO) 5 MoC(OEt)(Ar)] have the highest oxidation potentials, followed by the oxidation potential of [(CO) 4 (PPh 3 )MoC(OEt)(Ar)], while [(CO) 4 (AsPh 3 )MoC(OEt)(Ar)] oxidized at a potential 0.12 − 0.15 V lower than the PPh 3 substituted complexes [(CO) 4 (PPh 3 )MoC(OEt)(Ar)]. Substitution of carbonyl ligand(s) in the pentacarbonyl complexes 1 – 4 , by one (complexes 5 – 12 ) or two ([(dppe)(CO) 3 MoC(OEt)(2-furyl)] complex ( 13 ), dppe = 1,2-bis(diphenylphosphino)ethane) weaker π-acceptor ligands (phosphines/arsines) in Fischer carbene complexes leads to a decrease in the binding energy of the Mo 3d 5/2 photoelectron lines of the X-ray photoelectron spectra of the Fischer carbene complexes and an increase in the binding energy of the carbene carbon C 1 s photoelectron lines.
ABSTRACT The synthesis of a variety of tetrahedral β-diketonato titanium(IV) complexes of the typ... more ABSTRACT The synthesis of a variety of tetrahedral β-diketonato titanium(IV) complexes of the type [(C5H5)2Ti(CH3COCHCOR)]+ClO4- with R=CF3, OCH3, C6H5, CH3 and Fc is described. The TiIII/TiIV couples and the Fc/Fc+ couple exhibited chemically and electrochemically reversible cyclic voltammetric behaviour. The formal reduction potential of the TiIII/IV couple increased as the group electronegativity of the R group of the β-diketonato ligand increased. Bulk electrolysis showed that one electron was transferred in the TiIII/IV couple and one electron in the ferrocenyl/ferrocenium redox couple in the ligand. The crystal structure for the R=OCH3 complex showed that this β-keto-ester binds through the carbonyl oxygen of the ester group and not the ether oxygen.
Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diket... more Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diketonato) cobalt(III) complexes is more stable ( mer isomers are more stable because they are less affected by steric hindrance and they have lower dipoles). An excess of the mer isomer or only the mer isomer is experimentally observed. The existence of both fac and mer isomers is predicted by density functional theory calculations. At room temperature, the nuclear magnetic resonance peaks of phenyl-containing mer complexes are broad due to the intermediate rotation of bulky phenyl groups resulting in only the average orientation of the non-equivalent protons in the mer complexes. However, upon heating to 55 °C (thus speeding up the rotation) or cooling to −50 °C (slowing down the rotation), this broad peak is resolved into three sets of carbon peaks appearing in the 13C NMR spectrum, as well as splitting of the 1H NMR peaks for the non-equivalent protons in the mer isomer. In solid-state 1...
Abstract Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH2-CO-R were sy... more Abstract Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH2-CO-R were synthesised to obtain two β-diketones with R = CH3, 3, and R = Fc (ferrocenyl = FeII(C5H5)(C5H4)), 4, a β-ketoester, 5, with R = OEt and a β-ketoamide, 6, with R = NH2. The β-diketones exhibited keto ⇌ enol tautomerization with the enol form Fc-CO-CH=C(OH)-R as the dominant isomer. Both the β-ketoester and β-ketoamide primarily existed in the keto form. FTIR and 1H NMR measurements could distinguish between keto and enol isomers. Dilute CHCl3 solutions of 3 and 4 exhibited FTIR ѵC=O keto vibrations between 1627 and 1712 cm−1 and ѵC=O enol vibrations between 1590 and 1660 cm−1. X-ray photoelectron spectroscopic (XPS) measurements showed keto isomer Fe 2p3/2 photoelectron lines at smaller binding energies than enol isomers. Significantly lower calculated molecular energies of the keto form of the β-ketoester 5 and β-ketoamide 6 utilising the Gaussian09 suite of programs at the B3LYP (uB3LYP for open-shell species), confirmed that 5 and 6 almost exclusively exists in the keto conformation. Cyclic voltammetry also distinguished between keto and enol isomers, and it was found that the electrochemical reversible ferrocenyl formal oxidation potential, E°ꞌ, of keto isomers of compounds can be estimated with the equation E°ꞌketo = 170.99χR–57.57 where χR is the group electronegativities of R in FcCOCH2COR. This result complements earlier research that enables calculation of the ferrocenyl formal oxidation potentials of enol isomers of β-diketones. Computational studies further showed that the HOMO orbitals of 3–6 is exclusively on the Fe centre and computed Mulliken spin densities on the dxy orbital of the oxidised iron species approached 1 e−.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Langmuir : the ACS journal of surfaces and colloids, 2012
The bimetallic paddlewheel catalyst precursor, [Pd(II)Co(II)(μ-OOCCH(3))(4)] H(2)O·2CH(3)COOH (1)... more The bimetallic paddlewheel catalyst precursor, [Pd(II)Co(II)(μ-OOCCH(3))(4)] H(2)O·2CH(3)COOH (1), prepared from [Pd(3)(μ-OOCCH(3))(6)] and [Co(OOCCH(3))(2)], was used as a single source precursor to prepare, after binding to a surface-hydroxylated silicon wafer and oxidation, the bimetallic oxides of Pd(IV)Co(III)/SiO(2) catalyst supported on a model planar (i.e., two-dimensional) silicon wafer. This catalyst catalyzes the aerobic oxidation of alcohols to its corresponding carbonyl compounds. The bimetallic tetracarboxylato catalyst precursor was bonded to the surface-hydroxylated silicon wafer by spin-coating and also by grafting. X-ray photoelectron spectroscopy (XPS) revealed that one of the four μ-acetato bridging ligands was substituted by Si-O fragments in a covalent bond formation process during grafting of 1 onto the wafer. In contrast, during the spin-coating process, all four acetato ligands remained intact during fixation on the silicon surface. Upon oxidation and workup...
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