Intermolecular CH-π Electrons Interaction in Poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO): An Experimental and Theoretical Study.

Amin O. Elzupir,Khalid H. Ibnaouf,Rageh K. Hussein

doi:10.3390/molecules27051488

Amin O. Elzupir, Khalid H. Ibnaouf + Show 1 more

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https://doi.org/10.3390/molecules27051488

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Abstract

This study demonstrates the presence of CH-π 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 π-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-π 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–LUMO 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-π 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 π bonds in the aromatic rings of PFO-1.

Highlights

Conjugated polymers have become essential for researchers and scientists because of their high activity as materials in different disciplines in electronic and optoelectronic devices [1,2,3]
Researchers have become interested in studying the spectral properties of some conjugated polymers, the promising conjugated polymers of poly [9,9-dioctylfluorenyl2,7-diyl] (PFO-1) and poly [9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl] (PFO-2) (Figure 1)
The results showed that the n-alkyl side chain of the PFO-1 was straight and perpendicular to the funeral ring

Summary

Introduction

Conjugated polymers have become essential for researchers and scientists because of their high activity as materials in different disciplines in electronic and optoelectronic devices [1,2,3]. The main distinguishing feature of PFO-1 is that it contains an n-alkyl side chain, while PFO-2 has a branched alkyl side chain The literature discusses their structural features deeply in the ground and excited states, such as the effect of the molecular weight of PFO on the structure of a single chain and the formation of α and β phase conformations. Molecules 2022, 27, 1488 while PFO-2 has a branched alkyl side chain The literature discusses their structural features deeply in the ground and excited states, such as the effect of the molecular weig hoft of PFO on the structure of a single chain and the formation of α and β phase conformations. FTOo -s2h, ecdoulilgdhntootnptrhodesuecequdeimstieorns sa,nPdF/Oor-1agangrdegPaFtOes-.2Two esrheedstuligdh- t ieodnitnhethseeiqrugersotuionnds,aPnFdOe-x1caitneddPsFtaOte-2s,wpearyeinstgupdaierdticinultahreairttgernotuionndtaontdheexbcoitneddssrteastepso, npsaiybilneg foprarthtiecualgagrraetgteantitoionnattotrtibhuetbeodntdostrheespβopnhsiabsleecfoonr ftohremaagtgioreng. aTthioins watotrrikbudteemdotonstthreatβespehvais-e dceonncfeoromf athtieonp.reTsheins cweoorfktdheemCoHns-πtraitnetseeravcidtieonnceanodf tthheepcroesnefnircme aotfiothneaCnHal-yπsiinstoefrapcotiloynmaenrd PtFhOe -c1oninfitrhmeagtiroonuanndaslytasties.oFfuprothlyemrmeroPreF,Oth-1e iinnftlhueegnrcoeuonfdthsetaatelk. yFlugrtrhoeurpmaotrtea,cthheedintofluPeFnOce woafsthsetuadlkieydl ginrotueprmatstaocfhtehde tporPesFeOncwea(sPsFtOud-2ie) dorinabtesremncseo(fPthFOe p-1r)esoefntchee(PstFeOri-c2h) ionrdarbasnecnec.e F(uPrFthOe-r1m) oofret,htehseteerniecrhgiynbdaranndcge.apFsu,rmthoelremcuolraer, othrbeiteanles,rgHyObManOd–gLaUpMs,Omionlteecrualcatrioonr,baitnadls, chHaOrgMeOd–isLtrUibMuOtiointoefratchteiosen,paonlydmcherasrgweedriestcraiblcuutliaotnedo.fAthmesoelpecoulylamredroscwkienreg cmalocduelal tiendd.i-A camteosletchualtatrhdeobcaknidngatm4o3d7 enlminidsicautessedthbayt tahneinbtaenrdacatito4n3b7entwmeiesncCauHs-eπdbboyndasnofinPtFeOra-1c.tion between CH-π bonds of PFO-1

Experimental Section

Conclusions