The molecule 1-methyl-5-nitroindoline (MNI) demonstrates to be a suitable probe to detect the change of structure of liquid water by varying temperature. The relationship of the peak wavenumber of the first absorption band of this probe with temperature clearly shows a minimum at 43 °C that indicates a change of structure in the liquid water at ambient pressure. The plot of the MNI wavenumber peak absorption against the heat capacity of liquid water shows a temperature range (35–45 °C) that resembles the crossover temperature proposed by Mallamace et al. (Faraday Discuss. 2013,167, 95) from thermodynamic measurements (42 ± 5 °C). The crossover temperature range includes the so-called phase-transition temperature at 34.6 °C and 0.05 atm measured by Dougherty et al. (J. Phys. Chem. A2006,110, 7577–7580) and matches the temperature measured from solvatochromism by Catalán and Gonzalo (43 °C) (Chem. Phys. Lett., 2017,679, 86–89) as the origin of a structural change in liquid water.

中文翻译：

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分子1-甲基-5-硝基二氢吲哚探测液态水随温度的结构变化

1-甲基-5-硝基吲哚啉（MNI）分子被证明是检测温度变化引起的液态水结构变化的合适探针。该探针的第一个吸收带的峰值波数与温度的关系清楚地显示出在43°C时的最小值，表明在环境压力下液态水的结构发生了变化。MNI波数峰值吸收对液态水热容量的曲线图显示了一个温度范围（35–45°C），类似于Mallamace等人提出的交叉温度。（法拉第讨论。2013，167， 95），从热力学测量（42±5℃）。跨越温度范围包括由Dougherty等人测量的在34.6℃和0.05atm的所谓相变温度。（J.物理 化学 甲2006，110， 7577-7580），并通过加泰罗尼亚语和Gonzalo（43℃）（从溶剂化测量的温度相匹配化学物理快报，2017年，679， 86-89），如液体的结构变化的原点水。