Synthesis, Spectroscopy and Electrochemistry in Relation to DFT Computed Energies of Ferrocene- and Ruthenocene-Containing -Diketonato Iridium(III) Heteroleptic Complexes. Structure of [(2-Pyridylphenyl)2Ir(RcCOCHCOCH3].

A series of new ferrocene- and ruthenocene-containing iridium(III) heteroleptic complexes of the type [(ppy)2Ir(RCOCHCOR')], with ppy = 2-pyridylphenyl, R = Fc = FeII(η5-C5H4)(η5-C5H5) and R' = CH3 (1) or Fc (2), as well as R = Rc = RuII(η5-C5H4)(η5-C5H5) and R' = CH3 (3), Rc (4) or Fc (5) was synthesized via the reaction of appropriate metallocene-containing ß-diketonato ligands with [(ppy)2(-Cl)Ir]2. The single crystal structure of 3 (monoclinic, P21/n, Z = 4) is described. Complexes 1-5 absorb light strongly in the region 280-480 nm the metallocenyl -diketonato substituents quench phosphorescence in 1-5. Cyclic and square wave voltammetric studies in CH2Cl2/[N(nBu)4][B(C6F5)4] allowed observation of a reversible IrIII/IV redox couple as well as well-resolved ferrocenyl (Fc) and ruthenocenyl (Rc) one-electron transfer steps in 1-5. The sequence of redox events is in the order Fc oxidation, then IrIII oxidation and finally ruthenocene oxidation, all in one-electron transfer steps. Generation of IrIV quenched phosphorescence in 6, [(ppy)2Ir(H3CCOCHCOCH3)]. This study made it possible to predict the IrIII/IV formal reduction potential from Gordy scale group electronegativities, χR and/or ΣχR' of -diketonato pendent side groups as well as from DFT-calculated energies of the highest occupied molecular orbital of the species involved in the IrIII/IV oxidation at a 98 % accuracy level.

Can Electrochemical Measurements Be Used To Predict X-ray Photoelectron Spectroscopic Data? The Case of Ferrocenyl-ß-Diketonato Complexes of Manganese(III).

In order to better understand intramolecular communication between molecular fragments, a series of ferrocene-functionalized ß-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, 1, CH3, 2, Ph = C6H5, 3, and Fc = FeII(η5-C5H4)(η5-C5H5), 4, the mixed ligand ß-diketonato complex [Mn(FcCOCHCOFc)2(FcCOCHCOCH3)], 5, as well as the acac complex [Mn(CH3COCHCOCH3)3], 6, were subjected to an electrochemical and X-ray photoelectron spectroscopy (XPS) study. The ferrocenyl (FeII) and MnIII redox potentials, E°', and photoelectron lines were sufficiently resolved in each complex to demonstrate a linear correlation between E°' and group electronegativities of ligand R groups, χR, or ΣχR, as well as with binding energies of both the Fe 2p3/2 and Mn 2p3/2 photoelectron lines. These relationships are consistent with effective communication between molecular fragments of 1-5. From these relationships, prediction of Mn and Fe core electron binding energies in [Mn(R1COCHCOR2)3] complexes from known manganese and/or ferrocenyl redox potentials are, therefore, now possible. Ligand infrared carbonyl stretching frequencies were successfully related to binding energy as a measure of the energy required for inner-sphere reorganization. In particular it became possible to explain why, upon electrochemical oxidation or photoionization, the ferrocenyl FeII inner-shell of 1-5 needs more energy in complexes with ligands bearing electron-withdrawing (CF3) groups than in ligands bearing electron-donating groups such as ferrocenyl. The XPS determined entity Iratio (the ratio between the intensities of the satellite and main metal 2p3/2 photoelectron lines) is an indication not only of the amount of charge transferred, but also of the degree of inner-sphere reorganization. Just as for binding energy, the quantity Iratio was also found to be related to the energy requirements for the inner-sphere reorganization depicted by the vibrational frequency, vco.

Seven Chromisms Associated with Dithizone.

Variations in the electromagnetic wavelengths of absorption and reflection of molecules do not only make life colorful but also are often of central importance in solar energy conversion and optoelectronic information processing and transfer. Dithizone and its derivatives and complexes are, to our knowledge, probably the most "colorful" compound, being responsive to no less than seven different external stimuli that effect color change. Apart from a more detailed discussion of the cyclic voltammetry and observed electrochromism in the SCH3-substituted free ligand and mercury complex, concentratochromism, solvatochromism, halochromism, thermochromism, and chronochromism in the ligand, and photochromism in the carboxy-functionalized phenylmercury(II) complex are also presented here. Color changes are either associated with proton transfer or loss, or isomerization.

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

A series of ferrocenyl-functionalized ß-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, CH3, Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p3/2 and Fe 2p3/2 core-level photoelectron lines and their satellite structures. A charge-transfer process from the ß-diketonato ligand to the Mn(III) metal center is responsible for the prominent shake-up satellite peaks of the Mn 2p photoelectron lines and the shake-down satellite peaks of the Fe 2p photoelectron lines. Multiplet splitting simulations of the photoelectron lines of the Mn(III) center of [Mn(FcCOCHCOR)3] resemble the calculated Mn 2p3/2 envelope of Mn3+ ions well, indicating the Mn(III) centers are in the high spin state. XPS spectra of complexes with unsymmetrical ß-diketonato ligands (i.e., R not Fc) were described with two sets of multiplet splitting peaks representing fac and the more stable mer isomers respectively. Stronger electron-donating ligands stabilize fac more than mer isomers. The sum of group electronegativities, ΣχR, of the ß-diketonato pendant side groups influences the binding energies of the multiplet splitting and charge transfer peaks in both Mn and Fe 2p3/2 photoelectron lines, the ratio of satellite to main peak intensities, and the degree of covalence of the Mn-O bond.

Consequences of Electron-Density Manipulations on the X-ray Photoelectron Spectroscopic Properties of Ferrocenyl-ß-diketonato Complexes of Manganese(III). Structure of [Mn(FcCOCHCOCH3)3].

Reaction of [Mn3(OAc)6O·3H2O](+) (1) with ferrocenyl ß-diketones of the type FcCOCH2COR with R = CF3 (2a) and CH3 (2b), Ph = C6H5 (2c), and Fc = Fe(II)(η(5)-C5H4)(η(5)-C5H5) (2d) yielded a series of ferrocene-functionalized ß-diketonato manganese(III) complexes 3a-3d, respectively, of general formula [Mn(FcCOCHCOR)3]. The mixed-ligand ß-diketonato complex [Mn(FcCOCHCOFc)2(FcCOCHCOCH3)] (4) was obtained by reacting mixtures of diketones 2b and 2d with 1. A single-crystal X-ray structure determination of 3b (Z = 2, triclinic, space group P1̅) highlighted a weak axial elongating Jahn-Teller effect and a high degree of bond conjugation. An X-ray photoelectron spectroscopic study, by virtue of linear relationships between group electronegativities of ligand R groups, χR, or ∑χR, and binding energies of both the Fe 2p3/2 and Mn 2p3/2 photoelectron lines, confirmed communication between molecular fragments of 2a-2d as well as 3a-3d. This unprecedented observation allows prediction of binding energies from known ß-diketonato side group χR values.

Tetrabenzoporphyrin and -mono-, -cis-di- and Tetrabenzotriazaporphyrin Derivatives: Electrochemical and Spectroscopic Implications of meso CH Group Replacement with Nitrogen.

Nonperipherally hexyl-substituted metal-free tetrabenzoporphyrin (2H-TBP, 1a) tetrabenzomonoazaporphyrin (2H-TBMAP, 2a), tetrabenzo-cis-diazaporphyrin (2H-TBDAP, 3a), tetrabenzotriazaporphyrin (2H-TBTAP, 4a), and phthalocyanine (2H-Pc, 5a), as well as their copper complexes (1b-5b), were synthesized. As the number of meso nitrogen atoms increases from zero to four, λmax of the Q-band absorption peak becomes red-shifted by almost 100 nm, and extinction coefficients increased at least threefold. Simultaneously the blue-shifted Soret (UV) band substantially decreased in intensity. These changes were related to the relative electron-density of each macrocycle expressed as the group electronegativity sum of all meso N and CH atom groups, ∑χR. X-ray photoelectron spectroscopy differentiated between the three different types of macrocyclic nitrogen atoms (the Ninner, (NH)inner, and Nmeso) in the metal-free complexes. Binding energies of the Nmeso and Ninner,Cu atoms in copper chelates could not be resolved. Copper insertion lowered especially the cathodic redox potentials, while all four observed redox processes occurred at larger potentials as the number of meso nitrogens increased. Computational chemical methods using density functional theory confirmed 1b to exhibit a Cu(II) reduction prior to ring-based reductions, while for 2b, Cu(II) reduction is the first reductive step only if the nonperipheral substituents are hydrogen. When they are methyl groups, it is the second reduction process; when they are ethyl, propyl, or hexyl, it becomes the third reductive process. Spectro-electrochemical measurements showed redox processes were associated with a substantial change in intensity of at least two main absorbances (the Q and Soret bands) in the UV spectra of these compounds.

Electrochemical evidence of intramolecular electronic communication in Zr and Hf phthalocyanines bearing ferrocene-containing ß-diketonato axial ligands: structure of [PcHf(FcCOCHCOC6H5)2].

The series of zirconium(IV) and hafnium(IV) phthalocyanine complexes [PcM(FcCOCHCOR)2] (Pc = phthalocyaninato; M = Zr; R = CF3 (1), CH3 (2), C6H5 (3), Fc ((C5H5)Fe(C5H4), 4), as well as M = Hf ; R = CF3 (5), CH3 (6), C6H5 (7), and Fc (8)) were synthesized. A single-crystal X-ray diffraction analysis of the structure of [PcHf(FcCOCHCOC6H5)2], 7 (Z = 2, space group P1), showed the two axial ß-diketonato ligands were orientated in such a way that the ferrocenyl groups were positioned diagonally opposite each other. From the structural determination of 7 it was clear that these complexes have a distorted D4h symmetry at the coordination site of the metal centers, which explains a splitting of the UV-vis Q band into Qx and Qy components with 3 ≤ Δλ(max,Q) ≤ 10 nm. Cyclic and square wave voltammetric studies in CH2Cl2/[N((n)Bu)4][B(C6F5)4] allowed observation of at least three phthalocyaninato macrocycle-based redox couples as well as all (i.e., two or four) well-resolved ferrocenyl couples in 1-8. For M = Zr and R = Fc, formal reduction potentials of the four ferrocenyl groups were found to be E°' = 296, 386, 538, and 687 mV versus free ferrocene. Spectroelectrochemical evidence, UV-vis Q-band maximum wavelengths, and HOMO-LUMO energy gaps as expressed by ΔE°'I-III = ΔE°'wave I - ΔE°'wave III were mutually consistent, indicating that the first phthalocyaninato ring-based oxidation occurs before ferrocenyl oxidations take place. The potential for each redox process was found to be dependent on the sum of ß-diketonato R-group group electronegativities, ΣχR. Mathematical relationships for the dependency of E°' on ΣχR for all four observed ring-based redox processes as well as for the ferrocenyl-based redox processes were determined. This allowed prediction of potentials for redox processes that fall outside the workable potential window of the solvent. No significant differences were found between the corresponding redox potentials of zirconium and hafnium analogues bearing the same axial ligands.