title: 1H/31P distance determination by solid state NMR in multiple-spin systems.
abstract: The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S-I(k) commute with each other and no truncation takes place so that each addition of spin I(k) causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I(k) are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster.
authors.affiliation: Institut de Chimie, FRE 2446 CNRS, Université Louis Pasteur, BP 296, 67008 Strasbourg Cedex, France.
authors.forename: Maggy
authors.initials: M
authors.lastname: Hologne
authors.forename: Philippe
authors.initials: P
authors.lastname: Bertani
authors.forename: Thierry
authors.initials: T
authors.lastname: Azaïs
authors.forename: Christian
authors.initials: C
authors.lastname: Bonhomme
authors.forename: Jérôme
authors.initials: J
authors.lastname: Hirschinger