The dynamics and orientations of interlayer terephthalate (TA) anions in mixed-anion hydrotalcite-like compounds [Mg1-xAlx(OH)(2)](A(y)B(1-y))(x/2). nH(2)O, where A = p-C6D4(COO)(2)(2-) and B = CO32-] were investigated by H-2 variable-temperature solid-state nuclear magnetic resonance (NMR) spectroscopy. Two dominant 003 d spacings, 7.6 and 14.2 Angstrom, were observed by X-ray diffraction (XRD) in these samples, suggesting that there were at least two interlayer environments. Over the range of layer charges studied (0.37 greater than or equal to x greater than or equal to 0.29), the intensity of the 7.6 Angstrom XRD peak increased with decreasing x, while the intensity of the 14.2 Angstrom peak increased with increasing x. Analysis of H-2 NMR line shapes indicated that the motion of some of the TA anions in every sample could be described as rotational diffusion (RD) about the C-COO- axis at temperatures ranging from 245 to 355 K, with the remainder being essentially immobile. The fraction of TA anions exhibiting rotation (X-RD), as estimated by H-2 NMR, was positively correlated with the TA content of the interlayer and thus seemed to correspond to the fraction of TA molecules in the 14.2 Angstrom phase. A large difference in XRD was observed between compounds having similar layer charge but different TA mole fractions. At temperatures of less than or equal to 330 K, X-RD increased with temperature. A secondary minimum in X-RD, however, was observed for each of the compounds at temperatures between 330 and 350 K. We conclude that the presence of CO32-anions in the interlayer regions, rather than layer charge, is the dominant factor affecting the dynamics and orientation of interlayer TA anions.