Glasovac Zoran, Barić Danijela, Despotović Ines, Kovačević Borislav
Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia.
Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia.
Int J Mol Sci. 2025 May 24;26(11):5058. doi: 10.3390/ijms26115058.
Gas-phase basicity and basicity in acetonitrile solvent were investigated for a series of proton sponges derived from phosphazenyl phosphines. A range of aromatic and aliphatic scaffolds bearing phosphazenyl phosphine substituents were employed to modulate the basicity of these compounds, primarily by varying the distance between the phosphazenyl phosphine units. These proton sponges were shown to be exceptionally strong organic bases, with p values in acetonitrile reaching up to 42.0 units and gas-phase proton affinities (PA) up to 307.0 kcal mol. However, none exhibited higher basicity than the closely related phosphazenylphosphine systems, for which a p value of 43.8 and PA value of 307.5 kcal mol was previously reportedIt was found that the proton-chelating effect, typically defined as the difference in proton affinity between and -substituted systems (ΔPA), moderately influences basicity. However, it was also established that ΔPA should not be attributed exclusively to the elimination of electron-pair repulsion and the formation of hydrogen bond upon protonation, as has been commonly assumed in most previous studies of proton sponges, but must also account for mesomeric and inductive effects, as well as dispersion interactions.
对一系列源自磷腈基膦的质子海绵体，研究了其在气相中的碱度以及在乙腈溶剂中的碱度。采用了一系列带有磷腈基膦取代基的芳族和脂族骨架，主要通过改变磷腈基膦单元之间的距离来调节这些化合物的碱度。这些质子海绵体被证明是异常强的有机碱，在乙腈中的p值高达42.0个单位，气相质子亲和力（PA）高达307.0千卡/摩尔。然而，没有一个显示出比密切相关的磷腈基膦体系更高的碱度，之前报道该体系的p值为43.8，PA值为307.5千卡/摩尔。研究发现，质子螯合效应（通常定义为α-和β-取代体系之间的质子亲和力差异（ΔPA））对碱度有适度影响。然而，研究还确定，ΔPA不应像大多数之前质子海绵体研究中通常假设的那样，仅归因于消除电子对排斥和质子化时氢键的形成，还必须考虑中介效应和诱导效应以及色散相互作用。
