399. Mn-Th and Mn-Ce Tasos and Abhu ASAP (IC 2007)

399. Mn-Th and Mn-Ce Tasos and Abhu ASAP (IC 2007) - Inorg....

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
High-Nuclearity Ce/Mn and Th/Mn Cluster Chemistry: Preparation of Complexes with [Ce 4 Mn 10 O 10 (OMe) 6 ] 18 + and [Th 6 Mn 10 O 22 (OH) 2 ] 18 + Cores Abhudaya Mishra, ² Anastasios J. Tasiopoulos, ² Wolfgang Wernsdorfer, Khalil A. Abboud, ² and George Christou* Department of Chemistry, Uni V ersity of Florida, Gaines V ille, Florida 32611-7200, and Laboratoire Louis Ne ´ el-CNRS, BP 166, 25 A V enue des Martyrs, 38042 Grenoble, Cedex 9, France Received October 11, 2006 The syntheses, structures, and magnetic properties are reported of the mixed-metal complexes [Ce 4 Mn 10 O 10 (OMe) 6 (O 2 - CPh) 16 (NO 3 ) 2 (MeOH) 2 (H 2 O) 2 ]( 1 ) and [Th 6 Mn 10 O 22 (OH) 2 (O 2 CPh) 16 -(NO 3 ) 2 (H 2 O) 8 2 ), which were both prepared by the reaction of (NBu n 4 )[Mn 4 O 2 (O 2 CPh) 9 (H 2 O)] ( 3 ) with a source of the heterometal in MeCN/MeOH. Complexes 1 and 2 crystallize in the monoclinic space group C 2/ c and the triclinic space group P 1 h , respectively. Complex 1 consists of 10 Mn III ,2Ce III ,and2Ce IV atoms and possesses a very unusual tubular [Ce 4 Mn 10 O 10 (OMe) 6 ] 18 + core. Complex 2 consists of 10 Mn IV and6Th IV atoms and possesses a [Th 6 Mn 10 O 22 (OH) 2 ] 18 + core with the metal atoms arranged in layers with a 2:3:6:3:2 pattern. Peripheral ligation around the cores is provided by 16 bridging benzoates, 2 chelating nitrates, and either (i) 2 each of terminal H 2 O and MeOH groups in 1 or (ii) 8 terminal H 2 O groups in 2 . Complex 1 is the largest mixed-metal Ce/Mn cluster and the first 3d/4f cluster with mixed-valency in its lanthanide component, while complex 2 is the first Th/Mn cluster and the largest mixed transition metal/actinide cluster to date. Solid-state dc and ac magnetic susceptibility measurements on 1 and 2 establish that they possess S ) 4 and 3 ground states, respectively. Ac susceptibility studies on 1 revealed nonzero frequency-dependent out-of- phase ( l M ′′ ) signals at temperatures below 3 K; complex 2 displays no l M ′′ signals. However, single-crystal magnetization vs dc field scans at variable temperatures and variable sweep-rates down to 0.04 K on 1 revealed no noticeable hysteresis loops, except very minor ones at 0.04 K assignable to weak intermolecular interactions propagated by hydrogen bonds involving Ce III -bound ligands. Complex 1 is thus concluded not to be a single- molecule magnet (SMM), and the combined results thus represent a caveat against taking such ac signals as sufficient proof of a SMM. Introduction High-nuclearity transition metal cluster chemistry has been attracting intense interest during the last several years. This is due to the combination of the aesthetically pleasing structures that many such molecular clusters possess and the often unusual and even novel magnetic properties that some of them display. In particular, some of these clusters have been found to be single-molecule magnets (SMMs), which are individual molecules capable of functioning as nanoscale magnetic particles and which thus represent a molecular approach to nanomagnetism.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 01/22/2012.

Page1 / 11

399. Mn-Th and Mn-Ce Tasos and Abhu ASAP (IC 2007) - Inorg....

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online