{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,31]],"date-time":"2026-01-31T17:44:20Z","timestamp":1769881460306,"version":"3.49.0"},"reference-count":32,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2022,2,23]],"date-time":"2022-02-23T00:00:00Z","timestamp":1645574400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University","award":["RG-21-09-46"],"award-info":[{"award-number":["RG-21-09-46"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>This study demonstrates the presence of CH-\u03c0 interaction in poly [9,9-dioctylfluorenyl-2,7-diyl] (PFO-1) due to an aggregate formation of PFO-1 in the liquid state. The absorption spectra of PFO-1 in certain solvents at low concentrations showed a single band at 390 nm. However, when using high concentrations, a new band at 437 nm appeared. This band is due to the aggregate formation of PFO-1. The aggregate formation occurs as a result of the CH interaction of the n-alkyl side chains with \u03c0-electrons in the benzene ring. The optical characteristics of another conjugated polymer of poly [9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl] (PFO-2) were investigated to confirm the CH-\u03c0 interaction. The absorption showed only one wavelength at 390 nm without any new band at the end of the spectrum, even at higher concentrations and lower temperatures. The main reason for the absence of aggregate formation in PFO-2 is the sterical hindrance caused by the branched alkyl side chains. In addition, Density Functional Theory (DFT) was used to compute the HOMO\u2013LUMO transitions, electron charge distribution, and frontier molecular orbitals for each polymer. The Mulliken charge distribution and demonstrated a notable difference in the reactivity of the alkyl side chain, confirming the higher ability of PFO-1 to form CH-\u03c0 bonds. docking model emphasized that the band at 437 nm could be attributed to the interaction between CH in the n-alkyl side chain and \u03c0 bonds in the aromatic rings of PFO-1.<\/jats:p>","DOI":"10.3390\/molecules27051488","type":"journal-article","created":{"date-parts":[[2022,2,23]],"date-time":"2022-02-23T22:54:02Z","timestamp":1645656842000},"page":"1488","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Intermolecular CH-\u03c0 Electrons Interaction in Poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO): An Experimental and Theoretical Study"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5885-2981","authenticated-orcid":false,"given":"Amin O.","family":"Elzupir","sequence":"first","affiliation":[{"name":"Deanship of Scientific Research, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13318, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4497-9778","authenticated-orcid":false,"given":"Rageh K.","family":"Hussein","sequence":"additional","affiliation":[{"name":"Physics Department, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13318, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1146-9456","authenticated-orcid":false,"given":"Khalid H.","family":"Ibnaouf","sequence":"additional","affiliation":[{"name":"Physics Department, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13318, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,2,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1038\/16393","article-title":"Electroluminescence in conjugated polymers","volume":"397","author":"Friend","year":"1999","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5868","DOI":"10.1021\/cr900182s","article-title":"Synthesis of conjugated polymers for organic solar cell applications","volume":"109","author":"Cheng","year":"2009","journal-title":"Chem. 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