Selenoether macrocyclic chemistry—syntheses and properties of new potentially tridentate and hexadentate Se/O-donor macrocycles

Abstract

Treatment of O(CH2CH2SeCN)2 with Na in NH3(l), followed by dropwise addition of a thf solution of o-C6H4(CH2Br)2 at -40 degrees C leads to formation of three mixed Se/O-donor macrocycles which are separable by column chromatography, the [1 + 1] species L1, the [2 + 2] ring L2 and the [3 + 3] ring L3, of which L2 is by far the major species. Using the same starting materials, but in a high dilution cyclisation at room temperature with NaBH4 in thf/EtOH gives exclusively the [1 + 1] ring, L1. The saturated ring Se/O-donor macrocycles, L4 and L5 are obtained by simultaneous dropwise addition of solutions of O(CH2CH2SeCN)2 and Br(CH2)3Br to NaBH4 suspended in thf/EtOH. The small tridentate Se2O-donor ring, L4, is again the dominant product under these conditions (71%), although the more flexible precursors in this reaction also give rise to the larger Se4O2-donor ring, L5, as a by-product in 8% yield. These compounds are readily separated and purified by column chromatography (ethyl acetate:hexane, 1:19). The new macrocycles have been characterised by 1H, (13)C{1H} and (77)Se{1H} NMR spectroscopy and mass spectrometry, together with crystal structures of L1 and L2. Complexes of L1 and L2 with late transition metals (Pd(II), Pt(II), Cu(I) and Ag(I)) are also described.

Preparation and properties of cyclic and open-chain Sb/N-donor ligands

“…We have recently utilised a similar strategy for the preparation of a range of small ring selenoether macrocycles. 21,22…”

Coordination chemistry of macrocyclic ligands

“…A series of Se/O mixed donor macrocycles of varying ring sizes and incorporating ortho xylyl units, such as L 59 , have been synthesised by Reid and co-workers. 85 The smaller ring analogues forms 2:1 complexes copper(I) and silver(I) with two ligands present for each metal ion, however these appeared to be less stable than compounds formed with the larger ring chelators.…”

Macrocyclic Se4N2[7,7]ferrocenophane and Se2N[10]ferrocenophane containing benzyl unit: synthesis, complexation, crystal structures, electrochemical and optical properties

“…[5][6][7][8][9] The development of efficient chemosensors for heavy metal ions with biological and environmental interests is an area of intense activity in order to address practical needs, 10,11 such as Cu 2+ and Hg 2+ because of their bioaccumu-lation and toxicity. 12,13 The soft donor atom Se has been proven to coordinate well with late transition and heavy metal cations, [14][15][16][17][18][19][20][21][22] for example, Singh's group reported that Schiff base macrocycles with Se/Te can be good candidates for heavy metal cation sensing, while there exists a contradiction between stability and coordination of the selenium atoms prevented by larger selena Schiff base macrocycles. 14 Our group has embarked on the systematic study of multichannel probes based on macrocyclic polyselena [n]ferrocenophanes with the target to sense different kinds of metal cations.…”