Synthesis of meta and para-substituted aromatic sulfonate derivatives of polydentate phenylazaphosphinate ligands: enhancement of the water solubility of emissive europium(iii) EuroTracker® dyes

Abstract

Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Results and DiscussionThe target complexes ( Fig. 1) include three strongly absorbing and equivalent chromophores, in which there is meta or para-sulfonic acid substituent in the phenyl ring of the phosphinate moiety. The sulfonation of this position was not expected to perturb the chromophore characteristics significantly, as the phosphorus oxygen bond and the aryl groups to which it is attached are not strongly conjugated, unlike a trigonal amide or carboxylate substituent.Previous X-ray analysis studies of these phenylphosphinate lanthanide complexes have revealed that the phenyl rings are oriented in the same direction, away from the plane of the 9-N 3 ring, and with the same relative configuration at phosphorus. 13,15,16 These structural studies also confirmed that the phosphorus-oxygen double bond lies out of the plane of the aryl rings. A simple retrosynthetic analysis suggests the intermediacy of a 2,4,6-trisubstituted pyridine, with a 4-Br group, allowing a Sonogashira coupling reaction to an arylalkyne in a final ligand assembly step. the P centres respectively, as deduced by X-ray and CD studies on related systems. [13][14][15][16] OBC 2014 Delbianco 3In order to form the C-P bond, a palladium-catalysed reaction was envisaged, allowing insertion of a 2-pyridyl group into the P-H bond of a phenylphosphinic ester, bearing a suitably protected sulfonate group. Following the studies of Miller, 6a the behaviour of the trifluoroethyl and phenylsulfonate esters as protecting groups for the sulfonic acid moiety was examined; each ester was derived from 3 or 4-bromo-phenylsulfonyl chloride (Scheme 1).Palladium-catalysed coupling between the aryl bromide and anilinium hypophosphite proceeded in 70% yield for the trifluoroethyl ester, but failed with the phenyl ester, probably due to competitive insertion into the O-Ph bond. In this reaction, the added aminopropyltriethoxysilane serves as a base in the Pd-catalysed reaction, and enables the esterification of the phosphinic acid in situ. 17-19 Scheme 1The di-esters 3 and 4 were used in coupling reactions with 2-bromo-4-nitro-6-methyl pyridine in degassed toluene using Cl 2 Pd[bis(diphenylphosphino)ferrocene] as the catalyst to give the phosphinate esters 5 and 6 (Scheme 2). Bromination with neat acetyl bromide followed by reesterification of the phosphinic acid group with HC(OEt) 3 allowed the isolation of intermediates 7 and 8 in 77 and 81 % yield respectively. Treatme...

Advances in the lanthanide metallosupramolecular chemistry of the cucurbit[n]urils

“…For a given ligand system, isomorphic solid state products are common. A calorimetric study of the interaction of the lanthanide cations with Q [6] in aqueous formic acid confirmed that the values for the reaction enthalpies for the respective complexes are almost identical [64].…”

“…Five complexes were isolated with all but the fifth, a Yb 3+ complex (see below), containing K + . Each capsule included a bound nitrate ion in its cavity (the cavity of Q [5] is too small to include a [ReO 4 ] − anion, contrasting with Q [6] which is able to include this anion -see discussion in Section 3). In the first four complexes the lanthanide ion is nine-coordinate with a capped square antiprismatic geometry.…”

“…No single published review has systematically discussed lanthanide-Q[n] coordination chemistry since the first such species (a Sm 3+ -Q [6] complex) was reported by Fedin and co-workers in 2002 [65]. In this review we address this absence and present the lanthanide chemistry of the cucurbit[n]urils with emphasis on the more recent work.…”

“…In this review we address this absence and present the lanthanide chemistry of the cucurbit[n]urils with emphasis on the more recent work. Despite the first Ln 3+ -Q[n] complex being generated from Q [6], in the present discussion we start our discussion with the smallest member, Q [5] and then treat each of the larger homologues in turn.…”

“…Apart from the unique spectroscopic and magnetic properties, the lanthanides and their derivatives have numerous applications, including as NMR imaging agents [3,4], in optoelectronics applications [5], as luminescent materials (including probes in biology and medicine) [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], as new magnetic materials [20,21], as metal organic frameworks [22,23], as catalysts [24][25][26][27][28][29], and as vehicles for drug delivery in medicine [30,31]. Moreover, lanthanide species have been demonstrated be effective pharmaceuticals for the treatment of various diseases [32][33][34][35].…”