Evaluation of [Ln(H2cmp)(H2O)] Metal Organic Framework Materials for Potential Application as Magnetic Resonance Imaging Contrast Agents

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• 作者：Giovannia A. Pereira ; Joop A. Peters ; Filipe A. Almeida Paz ; Joo Rocha ; Carlos F. G. C. Geraldes
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：March 15, 2010
• 年：2010
• 卷：49
• 期：6
• 页码：2969-2974
• 全文大小：820K
• 年卷期：v.49,no.6(March 15, 2010)
• ISSN：1520-510X

文摘

Aqueous suspensions of metal organic frameworks (MOF) containing different Ln³⁺ ions, consisting of a series of layered Ln³⁺ networks formulated as [Ln(H₂cmp)(H₂O)] (where H₅cmp is (carboxymethyl)iminodi(methylphosphonic acid), with a relatively wide size distribution (400 nm to 1 μm) were studied by relaxometry. The water ¹H longitudinal (r₁) and transverse (r₂) relaxivities were obtained for aqueous suspensions of these materials with different lanthanide ions. The values of r₁ are very small and varied only slightly with the effective magnetic moment (μ_eff) of the lanthanide ions, while r₂ values are larger and proportional to the value of μ_eff². The dependence of R₂ on τ_CP (the time interval between two consecutive refocusing pulses in the train of 180° pulses applied in a CPMG pulse sequence) was evaluated. The value of R₂ initially increases with τ_CP and then saturates at higher τ_CP at a value that is about 3 to 5 times lower than R_2p*. This can be explained by the static dephasing regime (SDR) theory, in which the diffusion effect is taken into account and where the condition τ_D > Δω(r_p)⁻¹ holds (τ_D = r_p²/D, where D is the diffusion coefficient, r_p is the radius of the particle, and Δω(r_p) is the Larmor frequency shift at the particle’s surface). Separation of the particles into two fractions with different particle sizes led to a significant enhancement of the r₂ relaxivity of the smaller particles with a narrow size distribution. Magnetometric measurements performed with the particles containing Dy(III), Ho(III), and Gd(III) showed a typical paramagnetic behavior from 4 to 100 K, used to determine the Curie constants.