Allosteric pitch length tuning of a dinuclear double helicate

Baylies, Christian J.; Jeffery, John C.; Miller, Tom; Moon, Ryan; Rice, Craig R.; Riis‐Johannessen, Thomas

doi:10.1039/b506199g

Cited by 17 publications

(14 citation statements)

References 9 publications

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“…We have previously observed similar trends in a series of dicopper(II) doublestranded helicates, whose solid-state internuclear separations were found to depend on the size and charge of an s-block cation located in a remote crown ether binding site. [4] This disparity invokes the influences of other factors, arguably the most apparent of which is the accumulation of charge in the s-block cation bound complexes, that is, both helicate disassembly and pitch increase could be the result of electrostatic repulsion effects. Placing two crown etherbound Ba 2 + ions in close proximity to the dicopper(I) helicate core increases electrostatic repulsion within the complex and encourages the N-donor bound Cu I ions to move further apart.…”

Section: Discussionmentioning

confidence: 99%

“…s Block cation binding studies 4 ] 2 and L 1 was recorded before and after treatment with one equivalent of BaA C H T U N G T R E N N U N G (ClO 4 ) 2 ( Figure 3). Comparison of the spectra shows that whilst the aromatic region remains largely unaffected, the methylene protons (4.6 < d < 5.4) experience a significant change in both chemical shift and dynamic behaviour following addition of Ba 2 + ions; the initial singlet resonance being resolved into two doublets, both of which are shifted downfield by up to 0.4 ppm.…”

Section: Complex Of L 1 With Copper(i)mentioning

confidence: 99%

“…The remaining two sites are occupied by an acetonitrile molecule and a monodentate perchlorate anion. The ClO 4 À anion bridges to Na(2) in the adjacent molecule generating an infinite onedimensional chain of m-ClO 4 À -bridged cations which propagates along the crystallographic b axis. Including the bridging perchlorate, Na(2) is thus five-coordinate and interacts with only the outer four oxygens of the crown ether [Na-O (crown ether) separations in the range 2.319(7)-2.545(6) ].…”

Section: Srmentioning

confidence: 99%

“…[2] In binding to the crown ether macrocycles, the sblock cations essentially render the ligand unsuitable for sustaining the helicate assembly in the presence of Hg II ions. Furthermore, the same ligands preference for different metal ions [3] and the pitch-length of helicate complexes of a related ligand L 2 (see above) [4] have been modified by similar approaches.…”

Section: Introductionmentioning

confidence: 99%

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Ligand Reprogramming in Dinuclear Helicate Complexes: A Consequence of Allosteric or Electrostatic Effects?

Jeffery

Rice

Harding

et al. 2007

Chemistry A European J

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The ditopic ligand 6,6'-bis(4-methylthiazol-2-yl)-3,3'-([18]crown-6)-2,2'-bipyridine (L(1)) contains both a potentially tetradentate pyridyl-thiazole (py-tz) N-donor chain and an additional "external" crown ether binding site which spans the central 2,2'-bipyridine unit. In polar solvents (MeCN, MeNO(2)) this ligand forms complexes with Zn(II), Cd(II), Hg(II) and Cu(I) ions via coordination of the N donors to the metal ion. Reaction with both Hg(II) and Cu(I) ions results in the self-assembly of dinuclear double-stranded helicate complexes. The ligands are partitioned by rotation about the central py--py bond, such that each can coordinate to both metals as a bis-bidentate donor ligand. With Zn(II) ions a single-stranded mononuclear species is formed in which one ligand coordinates the metal ion in a planar tetradentate fashion. Reaction with Cd(II) ions gives rise to an equilibrium between both the dinuclear double-stranded helicate and the mononuclear species. These complexes can further coordinate s-block metal cations via the remote crown ether O-donor domains; a consequence of which are some remarkable changes in the binding modes of the N-donor domains. Reaction of the Hg(II)- or Cd(II)-containing helicate with either Ba(2+) or Sr(2+) ions effectively reprogrammes the ligand to form only the single-stranded heterobinuclear complexes [MM'(L(1))](4+) (M=Hg(II), Cd(II); M'=Ba(2+), Sr(2+)), where the transition and s-block cations reside in the N- and O-donor sites, respectively. In contrast, the same ions have only a minor structural impact on the Zn(II) species, which already exists as a single-stranded mononuclear complex. Similar reactions with the Cd(II) system result in a shift in equilibrium towards the single-stranded species, the extent of which depends on the size and charge of the s-block cation in question. Reaction of the dicopper(I) double-stranded helicate with Ba(2+) shows that the dinuclear structure still remains intact but the pitch length is significantly increased.

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Section: Discussionmentioning

confidence: 99%

Section: Complex Of L 1 With Copper(i)mentioning

confidence: 99%

Section: Srmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ligand Reprogramming in Dinuclear Helicate Complexes: A Consequence of Allosteric or Electrostatic Effects?

Jeffery

Rice

Harding

et al. 2007

Chemistry A European J

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“…The results reveal limitations to the use chiral ligands with hydrogen bond donor groups located for intermolecular hydrogen bonding for the selfassembly of helical coordination polymers and include the X-ray crystal structure of an unusual mixed-valent Cu(II) 2 Cu(I) trimer in which CuBr 2À 3 anion acts as a bridging ligand between the two Cu(II) centres.The predictable formation of helical coordination polymers is a contemporary challenge as these materials have applications spanning diverse areas such as asymmetric catalysis, chiral separations and optoelectronics [1][2][3][4][5][6][7][8][9][10][11]. We recently reported that helical copper(II) coordination polymers can be predictably constructed using hydrogen bonding interactions [4].…”

mentioning

confidence: 99%

Copper(I) tribromide dianion as a weakly-bridging, axial ligand: Synthesis of an unusual mixed-valent Cu(II)2Cu(I) trimer

Lonnon¹,

Craig²,

Colbran³

2006

Inorganic Chemistry Communications

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Allosteric‐Controlled Metal Specificity of a Ditopic Ligand

et al. 2005

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There are numerous examples in the field of metallosupramolecular chemistry that demonstrate that careful design of ligands can produce species that are selective to certain metal ions.[ [2] Another approach to enhance metal specificity is to introduce discrete binding domains within a ligand strand such that each domain is specific to a particular metal ion.[3] However, when using the latter strategies, the information contained within the ligand system, that is, its "programming", is finalized at the synthetic stage and cannot be altered thereafter. Herein, we describe a ditopic ligand L 1 , whose selectivity for different transition-metal ions can effectively be "reprogrammed" by the addition of the larger s-block-metal ions to the crown ether moiety. This approach is related to the allosteric effect demonstrated by Rebek et al., in which the ability of a crown ether to coordinate Group 1 metal ions is influenced by coordination of a remote bipyridine coordination domain. [4] In this case, however, the reverse occurs as coordination of the crown ether unit controls the ability of a remote nitrogendonor unit to act as either a tetradentate or bisbidentate domain. Other reprogrammable systems have been shown to control the formation of helicates [5] and modulate their pitch length. [6] The reaction of L 1 (Scheme 1) with an equimolar amount of [Cu(MeCN) 4 ]PF 6 in MeCN gave a dark-red solution, and ESI-mass-spectrometric analysis showed the formation of a dinuclear double helicate with an ion at m/z 1497 consistent with {[Cu 2 (L 1 ) 2 ](PF 6 )} + . In addition, the crown ether moiety

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Allosteric pitch length tuning of a dinuclear double helicate

Abstract: Self assembly of the ditopic ligand L1 with Cu2+ gives the dinuclear double helicate [Cu2(L1)2]4+, which can further coordinate s-block cations. This coordination alters the helicate pitch to a variety of different lengths depending on the size and charge of the guest cation.

Cited by 17 publications

References 9 publications

Ligand Reprogramming in Dinuclear Helicate Complexes: A Consequence of Allosteric or Electrostatic Effects?

Ligand Reprogramming in Dinuclear Helicate Complexes: A Consequence of Allosteric or Electrostatic Effects?

Copper(I) tribromide dianion as a weakly-bridging, axial ligand: Synthesis of an unusual mixed-valent Cu(II)2Cu(I) trimer

Allosteric‐Controlled Metal Specificity of a Ditopic Ligand

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