A new zinc (II) responsive MRI contrast agent

A new potential zinc-responsive gadolinium DO3A-based MRI contrast agent has been synthesized containing a picolinate acid group as an active arm. To study the complex properties, its emissive europium analogue has been prepared as a model. Changes in absorption and emission properties were observed as well as in the hydration number of the complex in response to increasing concentration of zinc (II). Further examination of the gadolinium complex showed a high relaxivity. In addition, a 32% modulation of relaxivity was observed in response to added zinc (II) ion which is beneficial as a zinc-responsive MRI contrast agent

A Binaphthyl-Containing Eu(III) Complex and its Interaction with Human Serum Albumin: A Luminescence Study

On binding to human serum albumin (HSA), the Eu(III) luminescent emission enhancement of a complex containing a binaphthyl chromophore enables the determination of binding constants, showing no chiral discrimination for the (R)- (K = 8200 ± 810 M[superscript −1]) and (S)-enantiomers (K = 7710 ± 460 M[superscript −1])

pH-Responsive Lanthanide Complexes Based on Reversible Ligation of a Diphenylphosphinamide

Ln-dpp-DO3A-based complexes [dpp is a pendant diphenylphosphinamide moiety and DO3A is 1,4,7-tris­(carboxymethyl)-1,4,7,10-tetraazacyclododecane] exhibit pH-responsive reversible ligation of the phosphinamide for both the gadolinium­(III) and europium­(III) analogues. p<i>K</i>_a values were 8.1 (±0.1) and 7.8 (±0.1) for <b>Gd.1</b> and <b>Gd.2</b>, respectively. The relaxivities (20 MHz, 298 K) of the gadolinium­(III) analogues were <i>r</i>₁ = 7.9 mM^–1 s^–1 (<b>Gd.1</b>) and <i>r</i>₁ = 8.2 mM^–1 s^–1 (<b>Gd.2</b>) in acidic media, corresponding to a hydration state <i>q</i> = 2; in basic media, deprotonation and coordination of the phosphinamide occurs, with <i>r</i>₁ = 5.4 mM^–1 s^–1 (<b>Gd.1</b>) and <i>r</i>₁ = 4.4 mM^–1 s^–1 (<b>Gd.2</b>) corresponding to <i>q</i> = 1. Sensitized luminescent emission was observed from the europium­(III) analogues following excitation at λ_ex = 270 nm. The hydration state values of the europium­(III) analogues were consistent with those of the gadolinium­(III) complexes, i.e., <i>q</i> = 1 and 2 in basic and acidic media, respectively. The ratio of the emission intensities of the Δ<i>J</i> = 1 and 2 bands enables concentration-independent reporting of the pH. Excited-state p<i>K</i>_a values were 8.3 (±0.1) and 8.5 (±0.1) for <b>Eu.1</b> and <b>Eu.2</b>, respectively

Pyridine imines as ligands in luminescent iridium complexes

Biscyclometallated iridium complexes [Ir(ppz)[subscript 2](X^Y)][PF[subscript 6]] (X^Y = pyridine imine) have been synthesised. The pyridineimine ligands are prepared in situ during the complexation. The complexes show room temperature emission between 640 and 780 nm in CH[subscript 2]Cl[subscript 2] solution. The emission is red shifted compared with the analogous bipyridine complex [Ir(ppz)[subscript 2](bipy)][PF[subscript 6]]. DFT calculations have been used to shed light on the influence of the imine substituent on the electrochemical and photochemical properties. In particular, the calculations suggests that there is a significant change in geometry between the ground state and the first triplet excited state for arylimines but not for alkylimines, leading to much weaker emission for the arylimine complexes. The work demonstrates that pyridineimines can be used as a substitute for bipyridines in luminescent iridium complexes