RESUMEN
The reactivity of the dilithioplumbole ([Li2(thf)2(µ,η5-LPb)], LPb = 1,4-bis-tert-butyl-dimethylsilyl-2,3-bis-phenyl-plumbolyl) towards the reactive pnictogen precursors P4, pentaphosphaferrocene, and pentaarsaferrocene ([Cp*Fe(η5-E5)] (Cp* = η5-C5Me5, E = P, As)) is reported. The reaction with P4 afforded a phospholyl lithium complex, via lead-phosphorus exchange, while the reactions with [Cp*Fe(η5-E5)] yielded the first examples of Pb-Fe-Li heterotrimetallic triple-decker polypnictogenides with three different deck motifs.
RESUMEN
Three different oxidovanadium(IV) porphyrin dimers with anti, cis, and trans arrangements of the two rings have been synthesized by changing the bridge between the porphyrin macrocycles. This provides a unique opportunity to investigate the role of the bridge and spatial arrangement between the two VIVO centers for their electronic communication and magnetic coupling. They were characterized by the combined application of XRD analysis, UV-vis and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility, and DFT calculations. One- and two-electron oxidations produce mono- and dication diradical species, respectively, which display an unusual ferromagnetic interaction between the unpaired spins of vanadium(IV) and porphyrin π-cation radical, in contrast to other metalloporphyrin dimers. The oxidized species show a dissimilar behavior between cis and trans isomers. The ferromagnetic coupling occurs between the porphyrin π-cation radical and the unpaired electron of the VIVO ion on the dxy orbital, orthogonal to the porphyrin-based molecular orbitals a1u and a2u.
RESUMEN
The effect of intermacrocyclic interactions was studied by controlled and stepwise oxidations of a monometallic silver(II) porphyrin dimer that contains a highly flexible ethane bridge. Monometallic dimers are unique systems and behave differently from their dimetallic analogues on the basis of their available sites for storing oxidizing equivalents. UV-visible spectrometry, 1 Hâ NMR spectroscopy, XPS and single crystal X-ray diffraction studies clearly suggest the removal of the first electron from the metal center. The removal of the second electron occurred from the ring center to form a π-cation radical and, thereby, form a very unique mixed-valent species. However, unlike in all other ethane-bridged metalloporphyrin dimers reported earlier, the 2e-oxidized species showed quite unusual structures depending on the nature of counter ions. Ions, such as SbF6 , SbCl6 and PF6 , are engaged in strong interactions with the porphyrin π-cation radical and causes substantial structural changes, including large deformation of the ring. The solid-state structure remains intact in solution as well. The observations are further supported by DFT calculations.
RESUMEN
Metallophilic interactions between closed-shell metal ions are becoming a popular tool for a variety of applications related to high-end materials. Heavier d8 transition-metal ions are also considered to have a closed shell and can be involved in such interactions. There is no systematic investigation so far to estimate the structure and energy characteristics of metallophilic interactions in AgII /AgII (d9 /d9 ), AgIII /AgIII (d8 /d8 ), and mixed-valent AgII /AgIII (d9 /d8 ) complexes, which have been demonstrated in the present study. Both interporphyrinic and intermetallic interactions were investigated on stepwise oxidation by using a rigid ethene-bridged cis silver(II) porphyrin dimer and the results compared with those for highly flexible ethane-bridged analogues. By controlling the nature of chemical oxidants and their stoichiometry, both 1e and 2e oxidations were done stepwise to generate AgII /AgIII mixed-valent and AgIII /AgIII porphyrin dimers, respectively. Unlike all other ethene-bridged metalloporphyrin dimers reported earlier, in which 2e oxidation stabilizes only the trans form, such an oxidation of silver(II) porphyrin dimer stabilizes only the cis form because of the metallophilic interaction. Besides silver(II)â
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silver(II) interactions in cis silver(II) porphyrin dimer, stepwise oxidations also enabled us to achieve various hitherto-unknown silver(II)â
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silver(III) and silver(III)â
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silver(III) interactions, which thereby allow significant modulation of their structure and properties. The strength of Agâ
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Ag interaction follows the order AgII /AgII (d9 /d9 )
RESUMEN
The interaction between two AgII porphyrins, connected covalently through a highly flexible ethane bridge, in a metalloporphyrin dimer has been investigated upon stepwise oxidation. X-ray structure determination of one and two-electron oxidized complexes has clearly revealed only metal-centered oxidation that results in short Ag-N (porphyrin) distance with large distortion in the porphyrin macrocycle. The 2e-oxidized complex exhibits significant metallophilic interaction in the form of a close AgIII â â â AgIII contact that brings two porphyrin rings more cofacial with syn-conformation, which would otherwise stabilize in an anti-form. The interaction also leads to an intense emission peak at 546â nm at 77â K in the photoluminescence study.