Diheptyloxy pv oligomers in solution: photoreactivity

Mechanistic studies on the photodegradation of 2,5-dialkyloxyl-substituted para-phenylenevinylene oligomers by singlet oxygen

“…Results have been previously reported on the photostability of 2,5-diheptyloxy-substituted PVoligomers in chloroform and cyclohexane, and the lower stability in the former solvent suggests the possible role of singlet oxygen in its degradation. 38 Gibson and Pochan have suggested that singlet oxygen may be a possible intermediate in the photodegradation of polyacetylene, 39 while Holdcroft described the reaction of poly(3alkylthiophenes) with singlet oxygen which was formed upon radiation of the polymer in presence of oxygen. 40, 41 However, Zhang and co-workers studied the photooxidative degradation of various poly(p-phenylenevinylene) model compounds, and suggested from studies with various sensitizers that singlet oxygen does not play the principal role in the process.…”

Synthesis of Well‐Defined Oligo(2,5‐dialkoxy‐1,4‐phenylene vinylene)s by Combined Olefin Metathesis and Wittig‐type Coupling: Effect of Conjugation Repeat Units and End Groups Toward Optical Properties

“…Even though the reactions were conducted both under high monomer concentration and under reduced pressure conditions, which should be more suited for this purpose, [ 5,6 ] the resultant materials were low-molecular-weight oligomers. It is thus assumed that, as demonstrated previously, [ 9 ] the reason for an obtainment of low-molecularweight oligomer may be due to the coordination of the ether oxygen of alkoxy group to the metal atom, which would stabilize carbene species as assumed in Scheme 2 (described in a bracket). [ 9 ] As demonstrated previously, [ 5,6 ] the resultant OPVs possessed exclusive trans selectivity as well as vinyl groups at the both polymer chain ends as confi rmed by 1 H NMR spectra (also see the Supporting Information).…”

“…The recorded fl uorescent spectra showed a vibronic splitting where the relative intensity of the S 1 → S 0 0-0 compared to the 0-1 electronic transition [ 9,21 ] seems to increase upon increasing conjugation length [ λ max : 532 nm ( 7PV-CHO ), 539 nm ( 15PV-CHO ), 540 nm ( 31PV-CHO )]. The intensity (in 7PV-CHO , and 15PV-CHO ) increased upon increasing the conjugation units, [ 16 ] but the intensity in 31PV-CHO became slightly lower than that in 15PV-CHO .…”

“…On the basis of our reported syntheses of poly(9,9-dialkylfl uorene-2,7-vinylene)s (PFVs), [ 5 ] PPVs [ 6 ] by the ADMET polymerization, [5][6][7][8][9][10][11] we explored a possibility for synthesis of high-molecular-weight oligomers/polymers in the presence of Ru catalyst under a reduced pressure Scheme 2 . [ 5b-d ] Two catalysts have been chosen, because catalyst A (called second-generation Hoveyda-Grubbs) was highly effective for synthesis of the above dialkyl-substituted PPVs, [ 6 ] and the modifi ed catalyst (catalyst B , called Zhan catalyst) was also effective in our initial screening.…”

“…[ 5e,g ] A formation of regular 1D conjugated structures on the nanoscale should be thus expected by adopting this methodology. [ 14,15 ] In contrast, it is well known that syntheses of oligo(2,5-dialkoxy-1,4-phenylene vinylene)s (OPVs) by the ADMET technique [ 9 ] affords a mixture of oligomers up to 7 (average 3) repeat units, [ 9b ] and the synthesis of high-molecular-weight oligomers seems diffi cult due to coordination of an oxygen atom toward the metal (Mo, Ru etc.) and/or accompanied catalyst decomposition.…”