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Ligand‐to‐Metal Ratio Controlled Assembly of Tetra‐ and Hexanuclear Clusters Towards Single‐Molecule Magnets
Author(s) -
Saalfrank Rolf W.,
Bernt Ingo,
Chowdhry Mubarik M.,
Hampel Frank,
Vaughan Gavin B. M.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010702)7:13<2765::aid-chem2765>3.0.co;2-8
Subject(s) - chemistry , ligand (biochemistry) , ferric , heteronuclear molecule , hydride , chloride , inorganic chemistry , crystallography , metal , medicinal chemistry , molecule , organic chemistry , biochemistry , receptor
A simple template‐mediated route, starting from triethalolamine 1 , sodium hydride or caesium carbonate, and iron( III ) chloride led to the six‐ and eight‐membered iron coronates [Na⊂{Fe 6 [N(CH 2 CH 2 O) 3 ] 6 }] + ( 2 ) and [Cs⊂{Fe 8 [N(CH 2 CH 2 O) 3 ] 8 }] + ( 3 ). In the reaction of N ‐methyldiethanolamine 4 (H 2 L 1 ) or N ‐(2,5‐dimethylbenzyl)iminodiethanol 6 (H 2 L 2 ) with calcium hydride followed by addition of a solution of iron( III ) chloride, the neutral unoccupied coronands [Fe 6 Cl 6 (L 1 ) 6 ] ( 5 ) and [Fe 6 Cl 6 (L 2 ) 6 ] ( 7 ) were formed. Subsequent exchange of the chloride ions of 7 by bromide or thiocyanate ions afforded the ferric wheels [Fe 6 Br 6 (L 2 ) 6 ] ( 8 ) or [Fe 6 (NCS) 6 (L 2 ) 6 ] ( 9 ), respectively. Titration experiments of solutions of dianion (L 1 ) 2− with iron( III ) chloride in THF revealed interesting mechanistic details about the self‐assembling process leading to 5 . At an iron/ligand ratio of 1:1.5 star‐shaped tetranuclear [Fe{Fe(L 1 ) 2 } 3 ] ( 11 ) was isolated. However, at an iron/ligand ratio of 1:2, complex 11 was transformed into the ferric wheel 5 . It was shown, that the interconversion of 5 and 11 is reversible. Based on the mechanistic studies, a procedure was developed which works for both the synthesis of homonuclear 11 and the star‐shaped heteronuclear clusters [Cr{Fe(L 1 ) 2 } 3 ] ( 12 ) and [Al{Fe(L 1 ) 2 } 3 ] ( 13 ). The structures of all new compounds were determined unequivocally by single‐crystal X‐ray analyses.