【正文】 at 290 nm, and the emission maximum(545 nm)was used to determine luminescence Tb(III)based emission spectra were measured using mM solutions of Tb plex analog in 100 mM HEPES buffer at pH in H2O and D2O in the absence and presence of Cu2+.The number of coordinated water molecules(q)was calculated according to eqn(2):62,63 q= 188。(1/T1)d + r1[M](1)where(1/T1)obs and(1/T1)d are the observed values in the presence and absence of the paramagnetic species, respectively, and [M] is the concentration of paramagnetic [Gd].Luminescence emission spectra were collected on a Hitachi uorescence luminescence lifetime was measured on a Lecroy Wave Runner 6100 Digital Oscilloscope(1 GHz)using a tunable laser(pulse width 188。H, 。N, 。 50 ns)as the excitation(Continuum Sunlite OPO).Mass spectra(MS)were obtained on an auto ex III TOF/TOF MALDIMS and anIonSpec ESIFTICR mass analyses were performed on a Vario EL Element Synthesis of pound 2,6bis(3(bromomethyl)1Hpyrazol1yl)isonicotinate(Compound1)59,60 and 4,7,10tris(2(tertbutoxy)2oxoethyl)4,7,10triazaazoniacyclododecan1ium bromide(Compound 2)61 were prepared following thereported 2( g, mmol)was suspended in 2 ml anhydrous acetonitrile with 6 equivalents of NaHCO3( g)and the mixture was stirred at room temperature for 1( g, mmol)was added, and the mixture was slowly heated to reflux(80 C)and stirred the reaction was terminated, the mixture was cooled to room temperature, and the solution was precipitate was washed several times with anhydrous acetonitrile, and the collected ltrate solution was evaporated under reduced residue was puried using silicagel column chromatography eluted with CH2Cl2–nhexane–CH3OH(10 : 3 : 1, v/v/v)to afford Compound 3( g, 53%)as a pale yellow NMR(600 MHz, DMSO): (s, 2H), (s, 2H), (s, 2H), (s, 4H), (s, 3H), (m, 4H), (m, 8H), (s, 8H), (m, 24H), (s, 54H)(?).13C NMR(151 MHz, CDCl3): d , , , , , , , , , , , , , , , , , , (?).HRMS(ESI): m/z C67H111N13O14 [M + 2H]2+ , [M + H + Na]2+ , [M + 2Na]2+ , found [M + 2H]2+ , [M+ H + Na]2+ , [M + 2Na]2+ (?).Synthesis of pound 3( g, mmol)was stirred with triuoroacetic acid in methylene chloride solution(2 ml)at room temperature for 24 solvent was then evaporated under reduced pressure, and the residue was washed three times in CH3OH and CH2Cl2 to eliminate excess obtained residue was dissolved with a minimum volume of CH3OH and precipitated with cold precipitate was ltered to afford a brown yellow solid( g).1H NMR(600 MHz, DMSO): (s, 2H), (s, 2H), (s, 2H), (s, 4H), (s, 3H), (b, 20H), (m, 24H)(?).13C NMR(151 MHz, D2O): d , , , , , , , , , , , , , , , , (?).MALDITOFMS spectrum(CH3OH): m/z C43H63N13O14 [M H] , found (?).Anal C43H63N13O14$3CF3COOH$2H2O: C, 。emission slit, 10 luminescence lifetime was measured on a Lecroy Wave Runner 6100 Digital Oscilloscope(1 GHz)using a tunable laser(pulse width 188。cycle time, 20 ms。dela time, ms。most of them have focused on the development of targeted, high relaxivity and bioactivated contrast responsive gadolinium(III)based MRI contrast agents can be modulated by particular in vivo stimuli including pH,28–35 metal ion concentration36–43 and enzyme –50 Notably, a number of copperresponsive MRI contrast agents have been reported to detect uctuations of copper ions in –58 These activated contrast agents exploit the modulation of the number of coordinated water molecules to generate distinct enhancements in longitudinal relaxivity in response to copper ions(Cu+ or Cu2+).In this study, we designed and synthesized a binuclear gadoliniumbased MRI contrast agent, [Gd2(DO3A)2BMPNA], that is specically responsive to Cu2+ over other biologicallyrelevant metal new copperresponsive MRI contrast agent prises two GdDO3A cores connected by a 2,6bis(3methyl1Hpyrazol1yl)isonicotinic acid scaffold59,60(BMPNA), which functions as a receptor for copperinduced relaxivity synthetic strategy for [Gd2(DO3A)2BMPNA] is depicted in Scheme , the T1 relaxivity of [Gd2(DO3A)2BMPNA] was studied at 25 C and 60 MHz in the absence or presence of Cu2+.Experiments to determine the selectivity of [Gd2(DO3A)2BMPNA] towards Cu2+ over other biologicallyrelevant ions were carried out as lifetime was measured to determine the number of coordinated water molecules(q)of [Gd2(DO3A)2BMPNA] in the absence or presence of Cu2+.In addition, T1weighted phantom images were collected to visualize the relaxivity enhancement caused by Cu2+, suggesting potential in vivo sectionMaterials and instrumentsAll materials for synthesis were purchased from mercial suppliers and used without further and 13C NMR spectra were taken on an AMX600 Bruker FTNMR spectrometer with tetramethylsilane(TMS)as an internal measurements were performed on a Hitachi Fluorescence timeresolved luminescence emission spectra were recorded on a PerkinElmer LS55 uorimeter with the following conditions: excitation wavelength, 295 nm。s metabolism and function more and more effective and agents are often used in MRI examinations to improve the resolution and sensitivity。s disease,6 amyotrophic lateral sclerosis,7,8 and prion ,10 Therefore, the assessment and understanding of the distribution of biological copper in living systems by noninvasive imaging is crucial to provide more insight into copper homeostasis and better understand the relationship between copper regulation and its physiological wide variety of organic uorescent dyes have been exploited for the optical detection of ions in the last few –13However, optical imaging using organic uorescent dyes hasseveral limitations such as photobleaching, light scattering,limited penetration, low spatial resolution and the disturbance of auto By parison, magnetic resonance imaging(MRI)is an increasingly accessible technique used as a noninvasive clinical diagnostic modality for medical diagnosis and biomedical It can provide high spatial resolution threedimensional anatomical images with information about physiological signals and bio