Kaljurand Ivari, Saame Jaan, Rodima Toomas, Koppel Ivar, Koppel Ilmar A, Kögel Julius F, Sundermeyer Jörg, Köhn Uwe, Coles Martyn P, Leito Ivo
Institute of Chemistry, University of Tartu , Ravila 14a Str, 50411 Tartu, Estonia.
Institute of Computer Sciences, University of Tartu , J. Liivi 2 Str, 50409 Tartu, Estonia.
J Phys Chem A. 2016 Apr 28;120(16):2591-604. doi: 10.1021/acs.jpca.6b01552. Epub 2016 Apr 19.
Experimental gas-phase superbasicity scale spanning 20 orders of magnitude and ranging from bicyclic guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene to triguanidinophosphazenes and P3 phosphazenes is presented together with solution basicity data in acetonitrile and tetrahydrofuran. The most basic compound in the scale-triguanidinophosphazene Et-N═P[N═C(NMe2)2]3-has the highest experimental gas-phase basicity of an organic base ever reported: 273.9 kcal mol(-1). The scale includes besides the higher homologues of classical superbasic phosphazenes and several guanidino-substituted phosphazenes also a number of recently introduced bisphosphazene and bis-guanidino proton sponges. This advancement was made possible by a newly designed Fourier transform ion cyclotron resonance (ICR) mass spectrometry setup with the unique ability to generate and control in the ICR cell sufficient vapor pressures of two delicate compounds having low volatility, which enables determining their basicity difference. The obtained experimental gas-phase and solution basicity data are analyzed in terms of structural and solvent effects and compared with data from theoretical calculations.
本文展示了一个跨越20个数量级的实验气相超强碱度标度，其范围从双环胍7-甲基-1,5,7-三氮杂双环[4.4.0]癸-5-烯到三胍基磷腈和P3磷腈，并给出了在乙腈和四氢呋喃中的溶液碱度数据。该标度中最强碱的化合物——三胍基磷腈Et-N═P[N═C(NMe2)2]3——具有有史以来报道的有机碱最高的实验气相碱度：273.9千卡/摩尔(-1)。该标度除了包括经典超强碱磷腈的高级同系物和几种胍基取代的磷腈外，还包括一些最近引入的双磷腈和双胍基质子海绵。这一进展得益于新设计的傅里叶变换离子回旋共振(ICR)质谱装置，该装置具有独特的能力，能够在ICR池中产生并控制两种低挥发性的精细化合物的足够蒸气压，从而能够确定它们的碱度差异。根据结构和溶剂效应分析了获得的实验气相和溶液碱度数据，并与理论计算数据进行了比较。
