{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,17]],"date-time":"2026-02-17T05:42:21Z","timestamp":1771306941455,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:00:00Z","timestamp":1760227200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202101230"],"award-info":[{"award-number":["KJQN202101230"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202201233"],"award-info":[{"award-number":["KJQN202201233"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202301203"],"award-info":[{"award-number":["KJQN202301203"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202301218"],"award-info":[{"award-number":["KJQN202301218"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202301219"],"award-info":[{"award-number":["KJQN202301219"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJQN202201246"],"award-info":[{"award-number":["KJQN202201246"]}]},{"name":"Foundation of Intelligent Ecotourism Subject Group of Chongqing Three Gorges University","award":["zhlv-20221010"],"award-info":[{"award-number":["zhlv-20221010"]}]},{"name":"Foundation of Intelligent Ecotourism Subject Group of Chongqing Three Gorges University","award":["zhlv-20221020"],"award-info":[{"award-number":["zhlv-20221020"]}]},{"name":"Scientific and Technological Research Program of Chongqing Municipal Education Commission","award":["KJZD-K202301203"],"award-info":[{"award-number":["KJZD-K202301203"]}]},{"name":"Natural Science Foundation of Chongqing, China","award":["CSTB2025TIAD-qykjggX0299"],"award-info":[{"award-number":["CSTB2025TIAD-qykjggX0299"]}]},{"name":"Natural Science Foundation of Chongqing, China","award":["CSTB2024NSCQ-LZX0169"],"award-info":[{"award-number":["CSTB2024NSCQ-LZX0169"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>This study reports the synthesis and comprehensive spectroscopic characterization of 4-indolylcyanamide (4ICA), a novel indole-derived infrared (IR) probe designed for assessing local microenvironments in biological systems. 4ICA was synthesized via a two-step procedure with an overall yield of 43%, and its structure was confirmed using high-resolution mass spectrometry and 1HNMR. Fourier Transform Infrared (FTIR) spectroscopy revealed that the cyanamide group stretching vibration of 4ICA exhibits exceptional solvent-dependent frequency shifts, significantly greater than those of conventional cyanoindole probes. A strong linear correlation was observed between the vibrational frequency and the combined Kamlet\u2013Taft parameter, underscoring the dominant role of solvent polarizability and hydrogen bond acceptance in modulating its spectroscopic behavior. Quantum chemical calculations employing density functional theory (DFT) with a conductor-like polarizable continuum model (CPCM) provided further insight into the solvatochromic shifts and suppression of Fermi resonance in high-polarity solvents such as DMSO. Additionally, IR pump\u2013probe measurements revealed short vibrational lifetimes (~1.35 ps in DMSO and ~1.13 ps in ethanol), indicative of efficient energy relaxation. With a transition dipole moment nearly twice that of traditional nitrile-based probes, 4ICA demonstrates enhanced sensitivity and signal intensity, establishing its potential as a powerful tool for site-specific environmental mapping in proteins and complex biological assemblies using nonlinear IR techniques.<\/jats:p>","DOI":"10.3390\/molecules30204063","type":"journal-article","created":{"date-parts":[[2025,10,15]],"date-time":"2025-10-15T06:06:32Z","timestamp":1760508392000},"page":"4063","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Synthesis and Characterization of 4-Indolylcyanamide: A Potential IR Probe for Local Environment"],"prefix":"10.3390","volume":"30","author":[{"given":"Min","family":"You","sequence":"first","affiliation":[{"name":"School of Computer Science and Engineering, Chongqing Three Gorges University, Chongqing 404100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qingxue","family":"Li","sequence":"additional","affiliation":[{"name":"School of Physics and Astronomy, Applied Optics Beijing Area Major Laboratory, Center for Advanced Quantum Studies, Beijing Normal University, Beijing 100875, China"},{"name":"Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zilin","family":"Gao","sequence":"additional","affiliation":[{"name":"School of Computer Science and Engineering, Chongqing Three Gorges University, Chongqing 404100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Changyuan","family":"Guo","sequence":"additional","affiliation":[{"name":"Key Laboratory of Intelligent Air-Ground Cooperative Control for Universities in Chongqing, College of Automation, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2863-5556","authenticated-orcid":false,"given":"Liang","family":"Zhou","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Thorium Energy, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1016\/j.ejmech.2013.06.012","article-title":"Synthesis and anticancer activity of 2,4-disubstituted furo [3,2-b] indole derivatives","volume":"66","author":"Zhuang","year":"2013","journal-title":"Eur. 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