Electrochemical Illumination of Intramolecular Communication in Ferrocene-Containingtris-β-Diketonato Aluminum(III) Complexes; Cytotoxicity of Al(FcCOCHCOCF₃)₃

Abstract

The series of ferrocene-containing tris-β-diketonato aluminum(III) complexes [Al(FcCOCHCOR)(3)] (R = CF(3), 1; CH(3), 2; C(6)H(5), 3; and Fc = ferrocenyl = Fe(η(5)-C(5)H(5))(η(5)-C(5)H(4)), 4) were synthesized and investigated structurally and electrochemically; complex 1 was subjected to cytotoxicity tests. (1)H NMR-spectroscopy distinguished between the mer and fac isomers of 2 and 3. Complex 1 existed only as the mer isomer. A single crystal X-ray crystallographic determination of the structure of a mer-isomer of Al(FcCOCHCOCF(3))(3), 1, (Z = 4, space group P2(1)2(1)2(1)) demonstrated extensive delocalization of all bonds which explained the pronounced electrochemically observed intramolecular communication between molecular fragments. In contrast to electrochemical studies in CH(2)Cl(2)/[N((n)Bu)(4)][PF(6)], the use of the supporting electrolyte [N((n)Bu)(4)][B(C(6)F(5))(4)] allowed identification of all Fc/Fc(+) electrochemical couples by cyclic and square wave voltammetry for 1-4. For R = Fc, formal reduction potentials of the six ferrocenyl groups were found to be E°' = 33, 123, 304, 432, 583, and 741 mV versus free ferrocene respectively. Complex 1 (IC(50) = 10.6 μmol dm(-3)) was less cytotoxic than the free FcCOCH(2)COCF(3) ligand having IC(50) = 6.8 μmol dm(-3) and approximately 2 orders of magnitude less toxic to human HeLa neoplastic cells than cisplatin (IC(50) = 0.19 μmol dm(-3)).

Properties of Manganese(III) Ferrocenyl-β-Diketonato Complexes Revealed by Charge Transfer and Multiplet Splitting in the Mn 2p and Fe 2p X-Ray Photoelectron Envelopes

“…0.4 eV higher binding energy than the peak of the mer isomer (solid lines), see Figure 2 and Table 1. The higher binding energy of the fac isomer is in agreement with published results [29], as well as experimental evidence of a similar Al compound, which showed that in solution only the mer isomer is present [43]. This implies that the mer isomer is more stable and in XPS the more stable isomer would be detected at the lowest binding energy.…”

Synthesis, Characterization, and Electrochemistry of Diferrocenyl β-Diketones, -Diketonates, and Pyrazoles

“…In addition, diferrocenyl diketone 5 was applied as a starting material for the synthesis of the titanium, iron, and boron β-diketonato coordination complexes 10 – 12 (pathway ii ), Scheme 2 . Therefore, following two synthetic methodologies were used: either ligand exchange [ 41 ] or lithium-halide metathesis. In this respect, coordination complex 10 was accessible by the addition of TiCl 4 to a tetrahydrofuran solution containing [Li(κ 2 O , O ′-FcC(O)CHC(O)Fc)] [ 41 ] at −80 °C, and 11 by refluxing [Fe(acac) 3 ] (acac = acetylacetonate) with a 3-fold excess of 5 in acetonitrile ( Scheme 2 ).…”

“…Therefore, following two synthetic methodologies were used: either ligand exchange [ 41 ] or lithium-halide metathesis. In this respect, coordination complex 10 was accessible by the addition of TiCl 4 to a tetrahydrofuran solution containing [Li(κ 2 O , O ′-FcC(O)CHC(O)Fc)] [ 41 ] at −80 °C, and 11 by refluxing [Fe(acac) 3 ] (acac = acetylacetonate) with a 3-fold excess of 5 in acetonitrile ( Scheme 2 ). For the preparation of the purple dioxaborine complex 12 , diisopropylamine and [BF 3 ∙Et 2 O] were subsequently reacted with 5 at ambient temperature.…”

“…In addition, they received great interest in the synthesis of (hetero)multimetallic complexes [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ] as catalysts in organic synthesis [ 30 , 31 , 32 ] and as anticancer drugs (especially copper and rhodium β-diketonates) [ 33 , 34 , 35 ]. Recently, they gained topical attention in the study of electron transfer processes, when, for example, redox-active groups such as ferrocenyls are present, i.e., in zirconium, hafnium, copper(I), copper(II), manganese, ruthenium, rhodium(I), and aluminum β-diketonate complexes [ 36 , 37 , 38 , 39 , 40 , 41 ].…”

Electrochemical and liquid crystal properties of ferrocene-based β-diketonato copper(II) and zinc(II) complexes

“…Numerous b-diketonate compounds with calamitic as well as non-calamitic structures, generated by a combination of the metal incorporated and the numbers of flexible chains, have been prepared and their mesomorphic properties investigated in detail [23][24][25][26][27][28][29][30]. However, ferrocene-containing b-diketones, widely used in conjugate chemistry [31] and medicinal chemistry, [32] etc., are rarely applied in the studies of metallomesogenic systems. Earlier, our research group utilized ferrocenyl long-chain alkyl b-diketones as ligands to coordinate with metal for obtaining heteropolynuclear mesogenic structures [33].…”