> Introduction

Vibrational frequencies of polyatomic molecules in the gas and condensed phases can be accurately measured with linear absorption and inelastic light scattering spectroscopy. The measured spectra are distinctively and differently dependent on molecular structure, conformation, dynamics, intermolecular interaction, and solute-solvent dynamics. Over the past decade, a variety of coherent nonlinear vibrational spectroscopic techniques such as multidimensional electronic, IR, THz, IR-Raman, IR-vis, vis-IR, and THz-Raman measurement methods have been developed, which enable researchers to study, via extracting information on ultrafast fluctuations of vibrational frequencies from experimental results, spontaneously fluctuating motions of surrounding solvent molecules, dynamical changes in local electrostatic environments, conformational transitions, chemical and biochemical reactions, solvation dynamics, protein structural dynamics and functions, characteristic processes of functional materials, and so on. The data generated through these experiments have inevitably required an interpretive method with atom-level chemical accuracy. Despite prolonged efforts to develop theories for describing vibrational solvatochromism and electrochromism as well as dynamic fluctuation of vibrational frequencies reflecting chemistry and biology of molecules of interest, still there is a lack of all-encompassing theory for vibrational solvatochromism not only because we still have to face with intrinsic complexity of intermolecular interactions between molecules in condensed phases but also because the vibrational frequency shifts induced by varying intermolecular interactions are very small quantities, e.g., fractions of thermal energy, that cannot be predicted nor described even with high-level quantum chemistry calculations or ab initio MD simulation methods. Over the past decade, to avoid such difficulties in quantitatively describing vibrational solvatochomic effects on molecular spectra, exceptionally successful empirical models, which have been referred to as vibrational frequency maps, based on rigorous theory of intermolecular interactions have been suggested, developed, and used to interpret experimental results on complicated molecular systems, which could not be described by any other means. The outcomes of all these investigations are a collection of vibrational frequency maps that have been successfully used to quantitatively describe vibrational frequency shifts and fluctuations of various peptide modes, small IR probe oscillators incorporated into proteins and functional materials, and so on. Despite the rapid growing number of vibrational frequency maps reported in literatures, there has not been any attempt to collect all the maps and make them available to every worker in this field.

Therefore, we have created this repository internet site, http://frequencymap.org, that can be considered as not only an open-access website for voluntarily depositing their vibrational frequency maps by developers themselves but also for discussing and updating recent developments and news in this research area.