File Name : fig.s1.tif

Caption : <b>fig. s1</b> simulated ir spectra of the most stable folded structures ac<sub>12</sub>, ac<sub>14</sub>, at<sub>11</sub> and at<sub>14</sub> at the b3lyp-d3 level with experimental results exp<sub>a</sub> and exp<sub>b</sub> for comparison. a lorentzian profile with a fwhm of 20 cm<sup>-1</sup> is used to convolute the calculated spectra.

File Name : fig.s2.tif

Caption : <b>fig. s2</b> simulated ir spectra of conformer at<sub>4</sub> at the b3lyp-d3 and m062x level with experimental results exp<sub>a</sub> and exp<sub>b</sub> for comparison. a lorentzian profile with a fwhm of 20 cm<sup>-1</sup> is used to convolute the calculated spectra.

File Name : fig.s3.tif

Caption : <b>fig. s3</b> the computed ir spectrum of representative conformer at<sub>1</sub> in the anharmonic motion (red) and the calibrated harmonic motion (black, scaling factor: 0.9813) at the b3lyp(bj)/6-311++g (d, p) level. a lorentzian profile with a fwhm of 20 cm<sup>-1</sup> is used to convolute the calculated spectra.