Silver(III)⋅⋅⋅Silver(III) Interactions that Stabilize the syn Form in a Porphyrin Dimer Upon Oxidation

Abstract

The interaction between two Ag 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 Ag ⋅⋅⋅Ag 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 546 nm at 77 K in the photoluminescence study.

Through‐Space Spin Coupling in a Silver(II) Porphyrin Dimer upon Stepwise Oxidations: AgII⋅⋅⋅AgII, AgII⋅⋅⋅AgIII, and AgIII⋅⋅⋅AgIIIMetallophilic Interactions

“…In most cases, oxidation at lower potential usually produces the porphyrin π‐cation radical . Recently, we have briefly reported in a communication the effects of stepwise oxidations of an Ag II porphyrin dimer in which two porphyrin rings are connected covalently through a highly flexible ethane bridge. Spectroscopic investigations revealed only metal‐centered oxidation in the porphyrin dimer.…”

“…Spectroscopic investigations revealed only metal‐centered oxidation in the porphyrin dimer. The 2e‐oxidized complex exhibits metallophilic interaction in the form of a close silver(III) ⋅⋅⋅ silver(III) contact that makes the two porphyrin rings more cofacial with syn conformation . An ethane linker, however, has significant horizontal and vertical flexibility and thus favors a slipped geometry of the complex, which would hinder possible through‐space interactions between the metal ions.…”

“…[1][2][3] Heavier d 8 transition-metal ions are considered to have a closed shell and have been shownt ob ei nvolved in metallophilic interactions. There are severalreports of argentophilic interactions with silver(I); [5] however,d ue to the open-shell configuration, no evidenceo fs uch interactions for silver(II) is claimed [2a] and only recently [6] we have shown evidence of Ag···Ag interactions with Ag III .S of ar,t here is no systematic investigation to estimatet he structure and energy characteristics of metallophilic interactions in Ag II /Ag II (d 9 /d 9 ), Ag III /Ag III (d 8 /d 8 ), and also mixed-valent Ag II /Ag III (d 9 /d 8 )c omplexes,w hich have been demonstrated in the presents tudy.…”

“…[11,12] In most cases, oxidation at lower potential usually produces the porphyrin p-cation radical. [11,12] Recently,w eh ave brieflyr eported in ac ommunication [6] the effects of stepwise oxidations of an Ag II porphyrin dimer in which two porphyrin rings are connected covalently throughahighly flexible ethane bridge. Spectroscopic investigationsr evealed only metal-centered oxidation in the porphyrin dimer.T he 2e-oxidized complex exhibits metallophilici nteraction in the form of ac lose silver(III)···silver(III) contact that makes the two porphyrin rings more cofacial with syn conformation.…”

Die Suche nach einkernigem Gold(II) und seine mögliche Rolle in Photokatalyse und Medizinalchemie

“…[54] Die Isolierung und vollständige Charakterisierung stabiler Gold(II)-Komplexe mit mindestens vier Donoratomen lässt es mçglich erscheinen, sogar bislang transiente,dreifach koordinierte,e inkernige Gold(II)-Spezies zu charakterisieren. Gemischtvalente Bis(porphyrinato)silber(II/III)-Dimere,die von Rath und Mitarbeitern hergestellt wurden, illustrieren dieses elegante Konzept fürd en Silberfall.…”