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Title: Solvent-dependent transition from concerted electron–proton to proton transfer in photoinduced reactions between phenols and polypyridine Ru complexes with proton-accepting sites

Journal Article · · Dalton Transactions
DOI:https://doi.org/10.1039/C8DT03858A· OSTI ID:1483559
ORCiD logo [1];  [1]; ORCiD logo [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
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The bimolecular rate coefficients ($$k_q^{obs}$$) for quenching the metal-to-ligand charge transfer excited states of two Ru polypyridine complexes containing H-bond accepting sites by six p-substituted phenols exhibit abrupt deviations from the expected linear correlations of log$$k_q^{obs}$$ with phenol’s Hammett σp constant. This pattern is attributed to a transition of the quenching mechanism from a concerted electron-proton transfer (EPT) to a proton transfer (PT); the latter becomes predominant for the most acidic phenols in MeCN, but not in CH2Cl2. This assertion is supported by a detailed thermochemical analysis, which also excludes the quenching pathways involving electron transfer from phenols with or without deprotonation of phenols to the solvent, either concerted or sequential. The transition from EPT to PT upon the σp increase is consistent/supported by the magnitudes of the measured and computed PhOH/OD kinetic isotope effects and by the observed reduction of the EPT product yields upon replacing the low σp methoxyphenol by the high σp nitrophenol. In addition to modulating the relative contribution of the EPT and PT quenching pathways, the solvent strongly affects the bimolecular rate coefficients for the EPT quenching proper. Unlike with H-atom transfer reactions, this kinetic solvent effect could not be quantitatively accounted for by the phenol-solvent H-bonding alone, which suggests a solvent effect on the H-bonding constants in the phenol-Ru complex precursor exciplexes and/or on the unimolecular EPT rate coefficients within these exciplexes.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC0012704
OSTI ID:
1483559
Alternate ID(s):
OSTI ID: 1479827
Report Number(s):
BNL-209492-2018-JAAM; ICHBD9
Journal Information:
Dalton Transactions, Vol. 47, Issue 44; ISSN 1477-9226
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 9 works
Citation information provided by
Web of Science

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Figures / Tables (43)

Chart 1(p. 4)figure Chart 1
Scheme 1(p. 5)figure Scheme 1
Table 1(p. 9)table Table 1
Table 2(p. 10)table Table 2
Figure 1(p. 11)figure Figure 1
Table 3(p. 13)table Table 3
Figure 2(p. 14)figure Figure 2
Scheme 2(p. 15)figure Scheme 2
Figure 3(p. 17)figure Figure 3
Figure 4(p. 19)figure Figure 4
Scheme 3(p. 19)figure Scheme 3
Figure 5(p. 21)figure Figure 5
Figure 6(p. 24)figure Figure 6
Figure S1.1(p. 34)figure Figure S1.1
Figure S1.2(p. 35)figure Figure S1.2
Figure S1.3(p. 36)figure Figure S1.3
Table S2.1(p. 39)table Table S2.1
Table S2.2(p. 42)table Table S2.2
Table S2.3(p. 44)table Table S2.3
Figure S2.1(p. 45)figure Figure S2.1
Figure S2.2(p. 46)figure Figure S2.2
Figure S2.3(p. 46)figure Figure S2.3
Figure S3.1(p. 48)figure Figure S3.1
Table S3.1(p. 48)table Table S3.1
Table S3.2(p. 49)table Table S3.2
Table S3.3(p. 50)table Table S3.3
Table S3.4(p. 51)table Table S3.4
Table S3.5(p. 52)table Table S3.5
Figure S3.2(p. 53)figure Figure S3.2
Table S3.6(p. 54)table Table S3.6
Figure S3.3(p. 56)figure Figure S3.3
Chart S4.1(p. 57)figure Chart S4.1
Table S4.1(p. 57)table Table S4.1
Scheme S5.1(p. 61)figure Scheme S5.1
Figure S5.1A-G Part 1(p. 62)figure Figure S5.1A-G Part 1
Figure S5.1A-G Part 2(p. 64)figure Figure S5.1A-G Part 2
Figure S5.2A-G Part 1(p. 66)figure Figure S5.2A-G Part 1
Figure S5.2A-G Part 2(p. 68)figure Figure S5.2A-G Part 2
Figure S5.3(p. 70)figure Figure S5.3
Table S5.1(p. 72)table Table S5.1
Figure S6.1(p. 73)figure Figure S6.1
Figure S6.2(p. 74)figure Figure S6.2
Figure S7.1(p. 76)figure Figure S7.1

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