title: Long-lived polarization protected by symmetry.
abstract: In this paper we elucidate, theoretically and experimentally, molecular motifs which permit Long-Lived Polarization Protected by Symmetry (LOLIPOPS). The basic assembly principle starts from a pair of chemically equivalent nuclei supporting a long-lived singlet state and is completed by coupling to additional pairs of spins. LOLIPOPS can be created in various sizes; here we review four-spin systems, introduce a group theory analysis of six-spin systems, and explore eight-spin systems by simulation. The focus is on AA'XnX'n spin systems, where typically the A spins are (15)N or (13)C and X spins are protons. We describe the symmetry of the accessed states, we detail the pulse sequences used to access these states, we quantify the fraction of polarization that can be stored as LOLIPOPS, we elucidate how to access the protected states from A or from X polarization and we examine the behavior of these spin systems upon introduction of a small chemical shift difference.
authors.affiliation: Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Yesu
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Theis
authors.affiliation: Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Tung-Lin
authors.initials: TL
authors.lastname: Wu
authors.affiliation: Department of Physics, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Claytor
authors.affiliation: Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Warren S
authors.initials: WS
authors.lastname: Warren
mesh_terms: D000480:Alkynes / Q000737:chemistry; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008299:Maleic Anhydrides / Q000737:chemistry; D008958:Models, Molecular; D011724:Pyridazines / Q000737:chemistry
chemical_list: D000480:Alkynes; D008299:Maleic Anhydrides; D011724:Pyridazines; C007474:2,3-dimethylmaleic anhydride