A Bis‐Manganese(II)–DOTA Complex for Pulsed Dipolar Spectroscopy1. Issue 13 (18th April 2016)

• Record Type: Journal Article
• Authors: Demay‐Drouhard, Paul; Ching, H. Y. Vincent; Akhmetzyanov, Dmitry; Guillot, Régis; Tabares, Leandro C.; Bertrand, Hélène C.; Policar, Clotilde
• Is Part Of: Chemphyschem. Volume 17:Issue 13(2016)
• Page Start: 2066
• Page End: 2078
• Publication Date: 2016-04-18
• Subjects: EPR spectroscopy -- gadolinium -- manganese -- pulsed electron–electron double resonance -- spin labels; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201600234
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: High‐spin gadolinium(III) and manganese(II) complexes have emerged as alternatives to standard nitroxide radical spin labels for measuring nanometric distances by using pulsed electron–electron double resonance (PELDOR or DEER) at high fields/frequencies. For certain complexes, particularly those with relatively small zero‐field splitting (ZFS) and short distances between the two metal centers, the pseudosecular term of the dipolar coupling Hamiltonian is non‐negligible. However, in general, the contribution from this term during conventional data analysis is masked by the flexibility of the molecule of interest and/or the long tethers connecting them to the spin labels. The efficient synthesis of a model system consisting of two [Mn(dota)] 2− (MnDOTA; DOTA 4− =1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetraacetate) directly connected to the ends of a central rodlike oligo(phenylene–ethynylene) (OPE) spacer is reported. The rigidity of the OPE is confirmed by Q‐band PELDOR measurements on a bis‐nitroxide analogue. The Mn II −Mn II distance distribution profile determined by W‐band PELDOR is in reasonable agreement with one simulated by using a simple rotamer analysis. The small degree of flexibility arising from the linking MnDOTA arm appears to outweigh the contribution from the pseudosecular term at this interspin distance. This study illustrates the potential of MnDOTA‐based spin labels for measuring fairly short nanometer distances, and also presents an interesting candidate for in‐depth studies of pulsed dipolar spectroscopy methods on Mn II −Mn II systems. Abstract : New labels for spin : The efficient synthesis of a model system consisting of two [Mn(dota)] 2− (DOTA 4− =1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetraacetate; see figure) molecules directly connected to a central rodlike oligo(phenylene–ethynylene) spacer is described. This study illustrates the potential of these spin labels for measuring short nanometer distances.