680190-95-8Relevant articles and documents
The Delicate Balance of Preorganisation and Adaptability in Multiply Bonded Host–Guest Complexes
von Krbek, Larissa K. S.,Achazi, Andreas J.,Schoder, Stefan,Gaedke, Marius,Biberger, Tobias,Paulus, Beate,Schalley, Christoph A.
supporting information, p. 2877 - 2883 (2017/03/08)
Rigidity and preorganisation are believed to be required for high affinity in multiply bonded supramolecular complexes as they help reduce the entropic penalty of the binding event. This comes at the price that such rigid complexes are sensitive to small geometric mismatches. In marked contrast, nature uses more flexible building blocks. Thus, one might consider putting the rigidity/high-affinity notion to the test. Multivalent crown/ammonium complexes are ideal for this purpose as the monovalent interaction is well understood. A series of divalent complexes with different spacer lengths and rigidities has thus been analysed to correlate chelate cooperativities and spacer properties. Too long spacers reduce chelate cooperativity compared to exactly matching ones. However, in contrast to expectation, flexible guests bind with chelate cooperativities clearly exceeding those of rigid structures. Flexible spacers adapt to small geometric host–guest mismatches. Spacer–spacer interactions help overcome the entropic penalty of conformational fixation during binding and a delicate balance of preorganisation and adaptability is at play in multivalent complexes.
Luminescence and Relaxometric Properties of Heteropolymetallic Metallostar Complexes with Selectively Incorporated Lanthanide(III) Ions
Ceulemans, Matthias,Debroye, Elke,Vander Elst, Luce,De Borggraeve, Wim,Parac-Vogt, Tatjana N.
, p. 4207 - 4216 (2015/09/15)
The synthesis and characterization of two diethylenetriaminepentaacetic acid (DTPA) based heteropolymetallic metallostar lanthanide complexes with the general formulas (GdL1)3Ln and (GdL2)3Ln are described. The
Degenerate molecular shuttles with flexible and rigid spacers
Guenbas, D. Deniz,Brouwer, Albert M.
experimental part, p. 5724 - 5735 (2012/09/05)
The preparation and dynamic behavior of degenerate rotaxane molecular shuttles are described in which a benzylic amide macrocycle moves back and forth between two naphthalimide-glycine units along a diphenylethyne spacer or an aliphatic spacer consisting of a C9, C12, or C 26 alkyl chain. Subtle differences in the 1H NMR spectra of the rotaxanes can be related to the presence of conformers in which the macrocycle interacts simultaneously with both glycines, especially in the case of the C9 spacer. The kinetic data of the shuttling behavior in the C26 rotaxane were obtained from dynamic NMR spectroscopy. The Eyring activation parameters were found to be ΔH? = 10 ± 1 kcal mol-1, ΔS? = -6.5 ± 2.0 cal mol-1 K-1, ΔG?298 = 11.9 ± 0.2 kcal mol-1. For the systems with the shorter spacers, the shuttling rates were higher. Also in the diphenylethyne, rotaxane shuttling is rapid on the NMR time scale, indicating that the rigid unit does not impose a large barrier to the translocation of the macrocycle.
