Dinuclear Palladium Complexes with Two Ligand‐Centered Radicals and a Single Bridging Ligand: Subtle Tuning of Magnetic Properties

Abstract

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. + ,w ith aP d-N-Pd angle close to 1278 (X-ray). Magnetic and EPR measurements indicatet wo independent S = 1 = 2 spin carriers and no magnetic interaction in the solid state. The two diradical species both show no spin exchange in solution,l ikely because of unhindered rotation around the PdÀXÀPd core. This work demonstrates that as ingle bridging atom can induce subtle and tunable changes in structural and magnetic properties of novel dinuclear Pd complexes featuring two ligand-based radicals.

Localized Mixed‐Valence and Redox Activity within a Triazole‐Bridged Dinucleating Ligand upon Coordination to Palladium

“…The experimental metricp arameters of 6 and 7 are well-reproduced by the DFT-optimized geometries in the closed-shell singlet (CSS), open-shell singlet (OSS), and triplet spin states. Similar to the non-tethered dinuclear diradical complexes with as ingle bridging (pseudo)halide ligand reported previously, [19] the OSS and triplet spin states lie very close in energy,w ith the former being slightly lower in energy (for 6: E OSS ÀE T = À0.15 kcal mol À1 ;f or 7: E OSS ÀE T = À0.19 kcal mol À1 ). The CSS solutionsa re 12.3 and 11.9 kcal mol À1 higher in energy than the OSS solutions for 6 and 7,r espectively.T he spin density plots of the OSS and triplet solutions for both systemsr eflect the diradical character of these systems (Figure 12).…”

“…[23] Brown's metrical oxidation state (MOS) method, which allowsf or quantification of the oxidation state of o-aminophenol-derived ligands by analysis of the CÀC, CÀO, andC ÀN bond lengths, [24] has proven to be areliable methodt ogain information about the ligand oxidation state in these Pd(NNO) complexes. [17][18][19] We typically find slight deviations for the NO AP oxidation state (MOS = À1.7 to À1.9) but these values are clearlyd iscernable from those corresponding to the NO ISQ oxidation state (MOS = À0.9 to À1.1). At first glance, the MOS valuesd onot to support the mixed-valence assignments for all the independentmolecules in the asymmetric units of 4 and 5, as some tend towardi ntermediate oxidation states for both rings.…”

“…Scheme4.One-electron oxidation of the ligand-based mixed-valence complexes 4 and 5 to form diradicals 6 and 7.R eagents and conditions:i )acetylferrocenium tetrafluoroborate, C 6 H 6 ,RT. to what was observed for mononuclear PdCl(NNO ISQ )u pon transformationt ot he corresponding azide complex. [19] Spectroelectrochemistry and time-dependent (TD)-DFT To gain insight into the reversible redox eventso bserved by cyclic voltammetry and to identifyt he envisaged IVCT transitions for the mixed-valences pecies, complexes 4 and 5 were studied by UV/Vis/NIR and FT/NIR/IR spectroelectrochemistry (SEC) by using an optically transparent thin-layer electrochemical (OTTLE) cell. As the spectroscopic data obtained for 4 and 5 is very similar,o nly results obtained with complex 5 will be discussed here, as the azide co-ligand offersa na dditional spectroscopic handle (data related to 4 can be found in the Supporting Information).…”

“…We previously reportedt he synthesis and properties of dinuclear Pd II complexes bearing either one redox-activep hosphine-appended PNO [17] or pyridine-appended NNO [18] ligand per Pd, with variousb ridging co-ligands. [19] The intramolecular spin-exchange coupling (J) [20] and d 8 -d 8 interaction between both Pd II centers were strongly influenced by the (pseudo)halide bridge( Figure 2). However,these complexes wereunstable to exogenous ligands or strongly coordinating solvents, which prevented detailed investigation into the intramolecular electron-transfer phenomena.…”

Metal–Metal Interactions in Heterobimetallic Complexes with Dinucleating Redox‐Active Ligands

“…Chemie computationally (see the Supporting Information, Table S1 for acomparison of the metric parameters). [15] Theopen-shell singlet (OSS) state of 3 is lower in energy than the corresponding closed-shell singlet (CSS) and triplet states by 36.1 and 10.2 kcal mol À1 ,r espectively.S imilarly,t he OSS state of 4 is lower in energy than the corresponding CSS and triplet states by 12.6 and 20.2 kcal mol À1 ,r espectively.S pindensity plots of the OSS solutions of 3 and 4 (Figure 3, top left and right) illustrate the presence of two ligand-centered radicals.A nalysis of the molecular orbitals show weak bonding interactions between aN id z 2 orbital and ar ehybridized d z 2 Àx 2 orbital on both Au atoms (Figure 3, bottom left and right). In agreement with the shorter AuÀNi distance observed for 4,abigger overlap was found for this orbital than for 3.T he filled antibonding orbitals,which are characteristic for d 8/10 -d 8/10 interactions,w ere also found at higher energy (see the Supporting Information).…”