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. 2020 Apr 4;142(16):7591–7597. doi: 10.1021/jacs.0c01712

Figure 2.

Figure 2

The infrared spectrum can be used as a proxy for the local molecular packing in the liquid or crystal. (a) Infrared spectra of liquid 1, liquid 2, crystal 1, and crystal 2 in the 1140–1250 cm–1 range. Liquid 1 shows a band with an intense peak at 1197 cm–1 and a shoulder at 1188.5 cm–1. During the LLT from liquid 1 to 2, one observes increased splitting of this band, which becomes even more pronounced in crystal 2. On the formation of crystal 1, the spectrum narrows, the peaks change intensity, while the shoulder remains in the same position as in liquid 1. (b) The final position of the intense peak is plotted as a function of quench temperature and is also shown (dotted lines) for liquid 1, crystal 1, and crystal 2. The data are fit to a sigmoid function shown as a solid line. (c) Normal-mode spectra for crystals 1, 2, and 3, as well as the uuu configuration of TPP. (d) Infrared image overlaying a bright field image of a droplet of liquid 2 produced at a quench temperature of 224 K. The color scale corresponds to the integrated area of the main peak in the interval 1200–1215 cm–1. Point spectra can be found in the SI, which match the bulk infrared measurements of liquid 1 and liquid 2.