Mali Gregor, Ristić Alenka, Kaucic Venceslav
National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia.
J Phys Chem B. 2005 Jun 2;109(21):10711-6. doi: 10.1021/jp050358n.
The incorporation of moderate amounts of Ni(II), Co(II), Fe(II/III), and Mn(II/III) into aluminophosphate zeotype AlPO4-34 and Fe(II/III) into aluminophosphate zeotype AlPO4-36 was studied by broadline 31P NMR. The technique provided direct evidence on isomorphous substitution of framework aluminum by transition metals and allowed us to determine the extent of the substitution. 31P NMR proved to be complementary to other spectroscopic techniques such as X-ray absorption spectroscopy (XAS), Mössbauer, electron paramagnetic resonance (EPR), and electron nuclear double resonance (ENDOR) spectroscopies. The position of the NMR signal belonging to phosphorus in the P(OAl)3(OMe) environment depended mostly on the magnitude of the hyperfine interaction between a phosphorus nucleus and an unpaired electron, which was delocalized from the transition metal atom Me by covalent bonding. The width of the NMR signal was dominated by dipolar coupling among phosphorus nuclei and nearest paramagnetic centers. In addition, broadline NMR of ethylenediamine-templated manganese phosphate (C2H10N2)[Mn2(HPO4)3(H2O)], which was used as a model compound, showed that on the basis of line positions and line widths different 31P signals could easily be assigned to different phosphorus crystallographic sites. The technique could thus be applied to extract valuable structural information about metal phosphates as well.
通过宽线³¹P NMR研究了将适量的Ni(II)、Co(II)、Fe(II/III)和Mn(II/III)掺入磷酸铝沸石型AlPO₄ - 34以及将Fe(II/III)掺入磷酸铝沸石型AlPO₄ - 36的情况。该技术提供了过渡金属同晶取代骨架铝的直接证据，并使我们能够确定取代程度。³¹P NMR被证明是对其他光谱技术（如X射线吸收光谱法（XAS）、穆斯堡尔谱、电子顺磁共振（EPR）和电子核双共振（ENDOR）光谱法）的补充。在P(OAl)₃(OMe)环境中属于磷的NMR信号的位置主要取决于磷核与未成对电子之间超精细相互作用的大小，该未成对电子通过共价键从过渡金属原子Me离域。NMR信号的宽度主要由磷核与最近的顺磁中心之间的偶极耦合决定。此外，用作模型化合物的乙二胺模板化磷酸锰（C₂H₁₀N₂)[Mn₂(HPO₄)₃(H₂O)]的宽线NMR表明，基于谱线位置和线宽，可以很容易地将不同的³¹P信号分配到不同的磷晶体学位置。因此，该技术也可用于提取有关金属磷酸盐的有价值的结构信息。
