π-Stacking attraction vs. electrostatic repulsion: competing supramolecular interactions in a tpphz-bridged Ru(ii)/Au(iii) complex

Abstract

The synthesis and characterization of a mixed metal ruthenium(II)/gold(III) complex bridged by tetrapyridophenazine (tpphz) are described. It is isostructural and isoelectronic to the well-known photocatalysts with palladium(II) or platinum(II). Concentration dependent 1 H-NMR spectroscopy and XRD studies show that the electrostatic repulsion between the gold(III) moieties exceeds the attractive π-stacking interaction.Theoretical calculations based on the new structural data confirm an increased positive charge on the bridging ligand as well as significantly altered orbital symmetry as compared to the previously investigated palladium(II) complex. This is the first example of a tpphz ruthenium(II) complex where π-stacking is completely inhibited. The detailed investigation of the solid-state structure showed for the first time in bimetallic tpphz bridged complexes no significant torsion within the bridging ligand itself. Although catalytic performance for proton reduction by gold(III) is naturally not observed, its photochemical decomposition in colloidal gold particles could be shown by TEM and DLS.

Excited state electron and energy relays in supramolecular dinuclear complexes revealed by ultrafast optical and X-ray transient absorption spectroscopy

“…However, this is not unprecedented; bending in L1 has also been reported in dinuclear structures bridging Ru(bpy) 2 with AuCl 2 or PdCl 2 . 52 , 53 These complexes had only slightly longer Ru–M distances than what we observe for CuH 2 –RuH 2 : 12.74 Å for Ru–Au and 12.70 Å for Ru–Pd.…”

“…One particularly versatile method for assembling multiple metal centers using tetrapyrido[3,2- a :2′,3′- c :3′′,2′′- h :2′′′,3′′′- j ]phenazine (tpphz) as a bridging ligand was first reported by Knapp et al 37 and Bolger et al 38 , 39 This ligand has been used as a building block for mono-, 38 di-, 37 , 38 tetra-, 40 – 42 and polynuclear 37 , 43 Ru( ii ) constructs as well as stereochemically pure, 44 asymmetric homodinuclear, 45 topological, 46 mixed valent, 47 and heterodinuclear 48 – 53 complexes. Additionally, the CuHETPHEN method pioneered by Schmittel et al 54 , 55 has been used by several groups, 56 – 69 including our own, 70 , 71 to prepare analytically pure heteroleptic Cu( i ) bis(phen) complexes (phen = 1,10-phenanthroline) that can serve as individual building blocks in the piecewise assembly of supramolecular constructs with absolute synthetic control.…”

Shedding Light on the Interactions of Hydrocarbon Ester Substituents upon Formation of Dimeric Titanium(IV) Triscatecholates in DMSO Solution

“…The methylene units are still buried in the groove of the helicate showing short distances to the neighboring catecholates (CH⋅⋅⋅C arom =2.9–3.3 Å), whereas the terminal alkene slightly sticks out of the vicinity of the dinuclear coordination compound. However, close distances between the internal sp 2 hybridized C alkene and C catechol atoms as low as 3.5 Å are observed and should result in some π–π repulsion …”

“…The core of the dimer is similar as described before for analogous hierarchically formed helicates. [25] The dimerization constantso ft he alkene complexes Li[Li 3 (2 3 Ti) 2 ]a re presented in Table 1and in Figure 9. The methylene units are stillburied in the groove of the helicateshowing short distances to the neighboring catecholates (CH···C arom = 2.9-3.3 ), whereas the terminal alkene slightly sticks out of the vicinity of the dinuclear coordination compound.…”

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a RuII(2,2′‐bpy)2 Derivative

“…In particular, the addition of extended aromatic ligands has been extensively studied for the corresponding Ru II complexes. Those works have given insight into the structure parameters that might affect the materials' performances of the compounds, and the compounds themselves remain highly relevant , . Beyond the already well‐studied π‐extended phenanthroline ligands, the introduction of the pyrazinacene‐type ligands to these dyes present some prospects for developing a series of highly fluorescent compounds whose substituents can be easily modified either at (bpy) 2 Ru II moiety (as has already been done) or at the pyrazinacene (here a fluorubine) moiety where lateral substitution at nitrogen atoms could be advantageous for tuning the interaction of the complexes with TiO 2 .…”