The shape of metallosupramolecular assemblies

Abstract

Despite original doubts on its feasibility, the control of the stereochemistry in ligand-bridged oligonuclear assemblies based on tris(bidentate) components has seen considerable progress in the last two decades, and differences have been observed in the physical characteristics of stereoisomers of such species. This retrospective review examines the background to this "stereochemical problem" and shows how the control of the stereochemical integrity of dinuclear and trinuclear ligand-bridged complexes has been utilised in studies of intramolecular electron transfer within the oligonuclear assemblies, and in probing the sequence- and structure-selectivity of the interaction of these species with nucleic acids.

CrIIIas an alternative to RuIIin metallo-supramolecular chemistry

“…S17 and Tables S31-S33 †) have surprisingly no precedent for analogous ruthenium complexes despite the intense activity dedicated to these specific supramolecular architectures. [19][20][21][22][23][24]69 The intermetallic separation is fixed to ca. 10.9 Å by the back-to-back bis(terpyridine) spacer (Fig.…”

“…The synthetic method developed by Housecroft and Constable 46 ] 3+ chromophores in linear dyads and triads, and in di-and tridimensional networks similar to those designed with Ru II . [19][20][21][22][23][24] While the assessment of the degree of communication between Ru II centres requires partial reduction to get mixed-valence systems, the paramagnetic and spin-only character of Cr III centres offers a straightforward access to this parameter with the simple determination of the isotropic magnetic coupling constants. For the [Cl 3 Cr(L)CrCl 3 ] and [(tpy)Cr(L)Cr(tpy)] 6+ dyads investigated here as proof-ofconcept, the distance dependence of the magnetic communication reveals subtle modulations due to ligand-field effects and orbital overlap, which are optimized when two CrN 6 chromophores are connected through an alkyne bridge in [(tpy)Cr(ebbt)Cr(tpy)] 6+ .…”

“…Despite its appealing electronic properties, Cr III has been scarcely introduced into polymetallic supramolecular architectures working as photonic devices, 17,18 whereas hundreds, if not thousands of sophisticated structures built with luminescent divalent ruthenium complexes have been designed and tested so far. [19][20][21][22][23][24] The main reason for this sidelining can be found in the Cr III coordination chemistry, which somehow mirrors that of trivalent cobalt with the formation of kinetically inert complexes as exemplified by the very small rate constants found for ligand exchange (e.g., k H 2 O = 2.4 × 10 −6 s −1 for [Cr(H 2 O) 6 ] 3+ ) 25 and for hydrolysis (e.g., k hydrolysis = 3.5 × 10 −4 s −1 for cis-[Cr(ethylenediamine) 2 Cl 2 ] + under acidic conditions). 26 Consequently, Cr III cannot be part of sophisticated multi-component self-assembly processes, in which structural self-healing under thermodynamic control is crucial.…”

Missing Building Blocks Defects in a Porous Hydrogen-bonded Amide-Imidazolate Network Proven by Positron Annihilation Lifetime Spectroscopy

“…IFP-14 was separated using the sieving technique. [17] We reported previously the synthesis of zinc or cobalt-L2 based H-bonded MBB networks [18,19] respectively, as minor products from the same reaction conditions and along with this, the L3 linker based MOFs IFP-7 and À8, respectively, as a major product. [18,19] We reasoned that the CE-synthetic conditions could be "thermodynamically" driven, allowing long time (6 days) for crystal growth in a reversible self-assembly synthesis process.…”

Differential Anticancer Activities of the Geometric Isomers of Dinuclear Iridium(III) Complexes

“…[24] However, there have been relatively few studies in which the biological properties of closely related geometric isomers of octahedral complexes have been examined. Reedijk and co-workers highlighted the potential importance of geometric isomers for [Ru(azpy) 2 Cl 2 ] {where azpy = 2-phenylazopyridine}, and related complexes, where one of the three isomers examined was more than ten times less cytotoxic than the other two isomers.…”