“…In this work, the vibrational properties of the CC bond in hexakis[(trimethylsilyl)ethynyl] benzene (HTEB, Figure a Insert), which has been used to synthesize hexaethynylbenzene, a precursor of graphdiyne, is examined using both the conventional IR, time-resolved infrared method and the femtosecond two-dimensional infrared (2D IR) method. − In recent years, the 2D IR method has been used to unravel ultrafast structural dynamics in condensed-phase molecular systems, ,− as well as in surface-immobilized molecular systems. − The time-resolved IR method, on the other hand, can yield vibrational relaxation dynamics as well as anisotropy dynamics. − Particularly, in 2D IR spectroscopy, a collection of 2D joint distributions of frequency fluctuations is shown and vary with the dynamical time (or waiting time). In a 2D IR spectrum, one part of the diagonal signal is the ν = 0 → ν = 1 transition (ν is vibrational quantum number), reflecting the autocorrelation of this transition frequency distribution, while the other part of the diagonal signal is the ν = 1 → ν = 2 transition, reflecting the cross-correlation of the 0 → 1 and 1 → 2 transition-frequency distributions.…”