Source of material: 4.0 g of 3-hydroxybenzaldehyde and 10 ml of acetic acid were heated to 323 K; 4 ml of bromine were added and stirred for 2 days after which 10 ml of water were added and the solution cooled to 277 K. The precipitate was ñltered and recristaUzed in CHCI3 (94% yield), 'н NMR (300 MHz, CDCI3) δ 10.16 (s, IH, СНО), 7.82 (s, IH, CH-Ar.), 4.40 (s, IH, О-Н). The structure was solved by direct methods. The hydrogen atoms were placed at calculated positions and refined as riding using the 8НЕЬХЬ93 defaults: O-H = 0.82 Â, C-H = 0.93 Â, U(H) = 1.2Uiso (parent atom). The examination of the crystal structure with PLATON92 (see ref. 7) showed that there are no solvent-accessible voids in the crystal lattice. There are two independent molecules in the assymetric unit cell, showed in the figure, with similar geometry. Bond lengths and angles are close to those of 2,4-dibromo-5-hydroxybenzaldehyde (see ref. 1). The rings are planar within 0.02 Л. The Br and 02 atoms of both molecules have small (< 0.1 Â) but significant deviation from the ring plane. The aldehydic groups are twisted around the C1-C7 bonds, probably as result of the intermolecular interactions described below. The twist angles (34.3(4)°, 27.4(5)°) are much larger than those observed in ref. 1. Table 3. Final atomic coordinates and displacement parameters (in A^) The molecules fomi infinite one-dimensional chains parallel to the α-axis via a H-bond between the hydroxyl and aldehydic groups: 02 -01(i): 2.857(10) Â, 02'···01'(ϋ): 2.907(11) λ where (i) 0.5+x, 1-y, ζ and (ii), 0.5+x,2-y, z. The H2 proton is also shared by an intramolecular H-bond between the hydroxyl ^up and the Br2 atom: 02·· Br2: 3,108 Â, 02' -Br2': 3,104(8) A.
Source of materialThe title compound was obtained from an aqueous solution of dimethylglycine and iron nitrate in a 3:1 proportion. After many months of room temperature evaporation of the solvent small single crystals were grown. They showed hygroscopic behaviour. Experimental detailsThe crystals were inserted in capillary and then tested by Laue photographic methods. The H atoms of the organic moieties were placed at calculated positions and refined as riding using SHELXL-97 [1] defaults. H atoms of the water molecules were not located. DiscussionThe title compound contains a triiron core linked by a m 3-bridging oxide ion. Trinuclear iron compounds are of interest because oxo-bridged polynuclear Fe(III) centres perform important biological functions, such as oxygen storage and transport in a variety of proteins. It has been established that the iron atoms in the Fe 3 O core are coupled antiferromagnetically both for Fe(III) and mixed valence (Fe(II)/Fe(III)), and spin frustation occurs due to the triangular geometry [2]. The magnetic Jahn-Teller effect has been observed in a few such compounds causing deviation of the clusters from an equilateral configuration [3].In the title compound, the (Fe 3O(dmgly)7(H2O)2) 7+ cation has no crystallographic imposed symmetry. Two of the Fe(III) ions are coordinated by four dimethylglycine molecules, one water molecule and the bridging oxide ion, while the third metal ion has the water molecule trans to the central oxide ion replaced by another dimethylglycine molecule. Each of the Fe(III) ions has a distorted octahedral geometry with distances to the basal planes of 0.192(2) Å, 0.101(2) Å and 0.202(2) Å for Fe1, Fe2, Fe3 respectively. The shortest Fe···Fe distance is 3.277(2) Å, too large to allow direct metal-metal interactions. A magnetic superexchange mechanism mainly through the central oxide ion has been used to explain the observed magnetic properties in similar compounds [2], the Fe-O1 distances range from 1.902(3) Å to 1.951(3) Å. The dimethylglycine molecules are present in neutral zwitterionic form, with the carboxylic group deprotonated and the amino group positively charged. The nitrate cations are disordered in the structure which accounts for their high displacement factors. One of the ions was refined in two different orientations. There is an extra dimethyl-glycine molecule that does not coordinate the metal core and its occupation refines to less than the unity. The oxygen atoms of four solvent water molecules were also located. These high solvent content and disorder is usual in these type of compounds [2]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.