Density functional theory calculations (B3LYP) were employed in the study of gas-phase basicity (GB) and pK_a of three different types of cyclic guanidines differing in the number of nitrogen atoms incorporated in rings. The large GB values were calculated for bigger ring sizes, and these guanidines fall within the superbases (GB > 240 kcal mol⁻¹). Basicity is associated with ring strain (decreasing the GB effect with an increase in strain), which is the least pronounced in guanidines with only one nitrogen atom incorporated in the ring. Study of geometrical and electronic parameters (the degree of pyramidalization of nitrogen atoms (DP), s-character of the lone pair and HOMA index) provided more detailed information on the ring strain effects.

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环状胍衍生物的气相碱度– DFT研究

密度泛函理论计算（B3LYP）用于研究三种不同类型的环状胍的气相碱度（GB）和p K _a，环状胍的氮原子数不同。对于较大的环尺寸，计算出较大的GB值，并且这些胍落入超碱基之内（GB> 240 kcal mol ^-1）。碱性与环应变有关（随着应变的增加而降低GB效应），这在只有一个氮原子掺入环的胍中最不明显。几何和电子参数（氮原子的锥体化程度（DP），孤对的S字符和HOMA指数）的研究提供了有关环应变效应的更详细信息。