A perchlorotriarylmethyl tricarboxylic acid radical 99% enriched in ¹³C at the central carbon (¹³C₁-PTMTC) was characterized in phosphate-buffered saline solution (pH = 7.2) (PBS) at ambient temperature. Samples immobilized in 1:1 PBS:glycerol or in 9:1 trehalose:sucrose were studied as a function of temperature. Isotope enrichment at C₁ creates a trityl that can be used to accurately measure microscopic viscosity. Understanding of the impact of the ¹³C hyperfine interaction on electron spin relaxation is important for application of this trityl in oximetry and distance measurements. The anisotropic ¹³C₁ hyperfine couplings (A_x = A_y = 24 ± 2 MHz, A_z = 200 ± 1 MHz) are larger than for the related ¹³C₁-perdeuterated Finland trityl (¹³C₁-dFT) and the g anisotropy (g_x = 2.0013, g_y = 2.0016, g_z = 2.0042) is slightly larger than for ¹³C₁-dFT. The tumbling correlation times (τ_R) for ¹³C₁-PTMTC are 0.20 ± 0.02 ns in PBS and 0.40 ± 0.05 ns in 3:1 PBS:glycerol, which are shorter than for ¹³C₁-dFT in the same solutions. T₁ for ¹³C₁-PTMTC is 3.5 ± 0.5 μs in PBS and 5.3 ± 0.4 μs in 3:1 PBS:glycerol, which are shorter than for ¹³C₁-dFT due to faster tumbling, larger anisotropy of the ¹³C₁ hyperfine, and about 30% larger contribution from the local mode. In immobilized samples, T₁ for ¹³C₁-PTMTC is similar to that for ¹³C₁-dFT and other trityls without chlorine or ¹³C₁ substituents, indicating that the ¹³C₁ and Cl substituents on the phenyl rings have little impact on T₁. The temperature dependence of T₁ was modeled with contributions from the direct, Raman, and local mode processes. Broadening of CW linewidths of about 0.6 G in fluid solution and about 2 G in rigid lattice is attributed to unresolved ^35,37Cl hyperfine couplings.

在环境温度下，在磷酸盐缓冲盐溶液 (pH = 7.2) (PBS) 中表征在中心碳 ( ¹³ C _{1 -PTMTC) 处富集}¹³ C 的全氯三芳基甲基三羧酸自由基 99% 。研究了固定在 1:1 PBS:甘油或 9:1 海藻糖:蔗糖中的样品作为温度的函数。_{C 1}的同位素富集产生三苯甲基，可用于精确测量微观粘度。了解¹³ C 超精细相互作用对电子自旋弛豫的影响对于这种三苯甲基在血氧测定和距离测量中的应用很重要。各向异性¹³ C ₁超精细耦合 ( A _x =  A _y  = 24 ± 2 MHz, A _z  = 200 ± 1 MHz) 大于相关的¹³ C ₁ -全氘化芬兰三苯甲基 ( ¹³ C ₁ -dFT) 和 g 各向异性 ( g _x  = 2.0013, g _y  = 2.0016, g _z  = 2.0042) 略大于¹³ C ₁ -dFT。¹³ C ₁ -PTMTC 的翻滚相关时间 ( τ _R )在 PBS 中为 0.20 ± 0.02 ns，在 3:1 PBS:glycerol 中为 0.40 ± 0.05 ns，比¹³ C _1短-dFT 在相同的解决方案中。¹³ C ₁ -PTMTC的T ₁在 PBS 中为 3.5 ± 0.5 μs，在 3:1 PBS:甘油中为 5.3 ± 0.4 μs，这比¹³ C _{1 -dFT 的短，这是因为}¹³ C ₁的翻滚速度更快，各向异性更大超精细，局部模式的贡献增加了约 30%。在固定化样品中，¹³ C ₁ -PTMTC的T _1与¹³ C ₁ -dFT 和其他不含氯或¹³ C ₁取代基的三苯甲基相似，表明¹³ C ₁苯环上的Cl取代基对T ₁影响不大。T ₁的温度依赖性是根据直接、拉曼和局部模式过程的贡献建模的。流体溶液中约 0.6 G 和刚性晶格中约 2 G 的 CW 线宽加宽归因于未解决的^35,37 Cl 超精细耦合。