Molecular Switches for any pH: A Systematic Study of the Versatile Coordination Behaviour of Cyclam Scorpionands

Lau, Yu Heng; Clegg, Jack K.; Price, Jason R.; Macquart, René B.; Todd, Matthew H.; Rutledge, Peter J.

doi:10.1002/chem.201703488

Cited by 13 publications

(19 citation statements)

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“…MeOH was purchased from Sigma Aldrich and stored over 3 Å molecular sieves. 1‐(6‐(1‐((2,6‐diisopropylphenyl)imino) ethyl)pyridin2‐yl)ethan‐1‐one, N‐(3‐(1,4,8,11‐tetraazacyclotetradecan‐1‐yl)propyl)‐1‐(6‐(1‐((2,6‐diisopropylphenyl)‐imino)ethyl)pyridin‐2‐yl)ethan‐1‐imine (PDIpCy), 1,4,8‐tris( tert ‐butoxycarbonyl)‐1,4,8,11‐tetraazacyclotetradecane, {2,6‐ 1‐(2‐aminoethyl)‐1,4,8,11‐tetraazacyclotetradecane, and [( i PrPDI)Fe(OTf) 2 ] were prepared according to literature procedures. Products were verified by NMR spectroscopy and mass spectrometry.…”

Section: Methodsmentioning

confidence: 99%

Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes

2020

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We present two bimetallic iron complexes, [Fe 2 (PDIeCy)(OTf ) 4 ] (1) and [Fe 2 (PDIpCy)(THF)(OTf ) 4 ] (2) coordinated by an unsymmetric ligand. The new ligand, PDIeCy (PDI = pyridyldiimine; e = ethyl; Cy = cyclam), is a variant of the previously reported PDIpCy (p = propyl) ligand, featuring a shorter linker between the two metal coordination sites. The structural and electronic properties of 1 and 2, both in the solid and solution state, were analyzed by means of X-ray crystallography, and spectroscopic methods, including 19 F-NMR. The two ligand platforms yield markedly different diiron structures: the PDIeCy ligand permits formation of a bridged, μ-OTf complex, while the [a] 499 two iron centers of the PDIpCy-based 2 remain unconnected, directly, under all conditions examined. Both compounds contain electronically non-coupled high-spin (S = 2) ferrous centers, as established by Mössbauer spectroscopy and magnetic susceptibility studies. Cyclic voltammetry demonstrates the rich redox chemistry of the compounds, involving both ligand and metal-centered redox processes. Moreover, we synthesized the two-electron reduced [Fe 2 (PDIeCy)] 2+ form of 1, which contains the dianionic PDI 2ligand, and represents a two-electron charge localized complex.group, to support dinuclear complexes thereof (Scheme 1). [29] We reported the synthesis of non-coupled homo-and heterobimetallic Ni-and Zn-containing PDIpCy complexes. We now have focused our attention on diiron compounds. Iron offers Scheme 1. Synthesis of 1 and 2.

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Section: Methodsmentioning

confidence: 99%

Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes

2020

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“…Olex2 depiction of complex cation 9A, trans-I-[Cu(9)](ClO4) + , with displacement ellipsoids shown at 50% probability level. Disordered sites are highlighted with 'faded' colours.…”

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“…Disordered sites are highlighted with 'faded' colours. The second perchlorate counterion is not shown.Crystal 9A was found to be that of a trans-I-[Cu(9)](ClO4) + complex cation(Figure 7and SIFigure SX4,Table 2and SITable SX2). The structure geometry is five-coordinate square pyramidal (τ = 0.03), with an axial perchlorate ligand and a coordinated cyclam adopting the favourable trans-I configuration.…”

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confidence: 99%

“…The coordinated perchlorate anion is disordered over two orientations (Figure SX4, SI), with coordination bond lengths of 2.359(9) Å for the major component and 2.301(17) Å for the minor component. The complex cation is pseudooligomeric, with the copper of one complex cation weakly interacting with the coordinated perchlorate of a second(Figure SX5, SI), with metal to neighbouring perchlorate oxygen distances of approximately 3.51 Å for the major perchlorate orientation and 3.68 Å for the minor orientation.Crystal 9B was found to comprise a pseudo-octahedral trans-III-[Cu(9)](ClO4)2 complex dication in which axial ligation involves necessarily weak alkyne π system coordination.…”

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confidence: 99%

“…Olex2 depictions of (a) complex 9C-1 trans-I-[Cu(9)](ClO 4 ) + and (b) complex dication 9C-2 trans-III-Cu(9)] 2+ , with displacement ellipsoids shown at the 50% probability level. The perchlorate counterions are not shown.…”

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Copper(II) Complexes of N-Propargyl Cyclam Ligands Reveal a Range of Coordination Modes and Colours, and Unexpected Reactivity

Counsell

Shi

et al. 2020

Preprint

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Herein we describe single crystal X-ray diffraction and spectroscopic investigations of the coordination chemistry of copper(II) complexes of cyclam derivatives with between 1 and 4 pendant alkynes. The crystal structures of these copper complexes unexpectedly reveal a range of coordination modes, and the surprising occurrence of five unique complexes within a single recrystallisation of the tetra-N-propargyl cyclam ligand. One of these species exhibits weak intramolecular copper-alkyne coordination, and another is formed by a surprising intramolecular copper-mediated hydroalkoxylation reaction with the solvent methanol, transforming one of the pendant alkynes to an enol ether. Multiple functionalisation of the tetra-N-propargyl ligand is demonstrated via a ‘tetra-click’ reaction with benzyl azide, and the copper-binding behaviour of the resulting tetra-triazole ligand is characterised spectroscopically.

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Scorpiands: Quinquedentate Ligands that Couple the Rigidity of Cyclam and the Flexibility of a Coordinating Side Chain

Fabbrizzi

2022

Eur J Inorg Chem

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This review tells the story of scorpiands, polyamine ligands which, when specifically stimulated, act as scorpions, and of their metal complexes, scorpiates. Scorpiands consist of a tetramine macrocycle (typically cyclam) capable of firmly including a transition metal and of a side chain ending with a nitrogen containing coordinating group: under unperturbed conditions the coordinating group is bound to the metal (ON), but on addition of acid the nitrogen is protonated and comes off the metal (OFF). Alternating acid/base addition makes the side chain move imitating the tail of a scorpion that bites a prey firmly immobilized by the claws. Occurrence of the ON-OFF motion is monitored by the colour change of the scorpiate complexes associated to the change of coordination or by fluorescence quenching/restoring when a light-emitting substituent is linked to the side arm. Scorpiate complexes can be considered optical molecular switches and, from a different standpoint, molecular machines able to convert chemical energy into mechanical work.

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Molecular Switches for any pH: A Systematic Study of the Versatile Coordination Behaviour of Cyclam Scorpionands

Cited by 13 publications

References 70 publications

Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes

Structural Differences and Redox Properties of Unsymmetric Diiron PDIxCy Complexes

Copper(II) Complexes of N-Propargyl Cyclam Ligands Reveal a Range of Coordination Modes and Colours, and Unexpected Reactivity

Scorpiands: Quinquedentate Ligands that Couple the Rigidity of Cyclam and the Flexibility of a Coordinating Side Chain

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