Highly Luminescent, Visible-Emitting Lanthanide Macrocyclic Chelates Stable in Water and Derived from the Cyclen Framework

Abstract

Two new tetraazamacrocyclic ligands are designed with the aim of sensitizing the luminescence of Tb(III) and Eu(III) ions in water: L5 [1,4,7,10-tetrakis[N-(phenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane] and L6 [1,4,7,10-tetrakis[N-(4-phenylphenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane]. These ligands react with lanthanide trifluoromethanesulfonates to yield stable 1:1 complexes in water (log K = 12.89 +/- 0.15 for EuL5). X-ray diffraction on [Tb(L5)(H(2)O)](CF(3)SO(3))(3) (P1 macro, a = 13.308(3) A, b = 14.338(3) A, c = 16.130(3) A, alpha = 101.37(3) degrees, beta = 96.16(3) degrees, gamma = 98.60(3) degrees ) shows the Tb(III) ion lying on a C(4) axis and being 9-coordinate, with one water molecule bound in its inner coordination sphere. The absolute quantum yields are determined in aerated water for the complexes formed with ions used in fluoroimmunoassays (Ln = Sm, Eu, Tb, and Dy). Large values are found for [Tb(H(2)O)(L5)](3+) and [Eu(H(2)O)(L6)](3+), in line with the molecular design of the receptors: 23.1% and 24.7%, respectively. The intense luminescence of these ions results from efficient intersystem crossing and L --> Ln energy transfer processes, as well as from a suitable shielding of the emitting ions from radiationless deactivation.

Tuning the Stoichiometry of Lanthanide Complexes with Calixarenes: Bimetallic Complexes with a Calix[6]arene Bearing Ether‐Amide Pendant Arms

“…Lifetimes of solutions (data reported are averages of at least five determinations), and quantum yields were measured with the same instrument. The quantum yield of the metal-centered luminescence was determined in degassed and anhydrous CH 3 CN at room temperature with respect to [Eu(L)] 3ϩ 3 ϫ 10 Ϫ5  in acetonitrile (Q abs ϭ 23% [39] ) where L is a cyclen derivative {1,3,7,10-tetrakis[N-(4-phenylacetyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane} using the following formula: where the subscript r stands for the reference, and x for the sample. A is the absorbance at the excitation wavelength λ, n the refractive index (1.344 for solution in CH 3 CN and 1.333 for the solution in water), and D the integrated luminescence intensity.…”

Non‐Cytotoxic, Bifunctional EuIII and TbIII Luminescent Macrocyclic Complexes for Luminescence Resonant Energy‐Transfer Experiments

“…[29,30] The carboxylic acid substituent 1 was obtained from bromoacetyl bromide and 6-aminocaproic acid (Scheme 2), while the phenacyl pendant 3 was synthesised as previously described. [25] One amine function of cyclen was protected by the method of Platzek et al for 1,7-substituted cyclens: [31] N,N-dimethylformamide dimethylacetal (DMF-DMA) was treated with cyclen to produce 1,4,7,10-tetraazatricyclo- A C H T U N G T R E N N U N G [5.5.1.0]tridecane (2 a) in almost quantitative yield and upon careful hydrolysis at low temperature this produced the formaldehyde-protected material 2 b. Use of a quasistoichiometric quantity of DMF-DMA (1.05 equivalents) resulted in avoidance of the formation of the diformylated product.…”

“…[18,19] In our laboratories, we pursue the development of visible [20] and near-infrared [21] luminescent probes through several strategies, one of which is based on dtma derivatives (Scheme 1). [22,23] [25] Building on the latter work, we have now replaced one phenacyl substituent with an aliphatic chain bearing a carboxylic acid function; this group, along with primary amine, chlorosulfonyl and isothiocyanate, is among the most common linking moieties that can covalently interact with biologically relevant molecules such as proteins. [26] The aim of this study is to examine the influence of this substitution on both the thermodynamic and photophysical properties of the resulting lanthanide complexes.…”

“…[25] The absorption maximum occurs at 247 nm (35 090 cm ); non observation of singlet-state fluorescence points to efficient non-radiative and/or intersystem crossing (isc) processes taking place in this molecule. The tripletstate energy is not much affected by the complexation; on the other hand, the phosphorescence spectra display a better intensity due to the heavy-atom effect of the lanthanide ion.…”

Lanthanide Chelates Based on Diethylenetriamine Fitted with O‐Benzoic Acid Pendant Arms

“…( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) organised (macrocyclic) [10] or predisposed receptors, [11,12] leading to induced cavities; these receptors can also be obtained by self-assembly processes [13] or by the use of flexible podands. [14] These latter are readily available, cheap and are easy to derivatize.…”