Substitution Effects of C-C Triple Bonds on Deactivation Processes from the Fluorescent State of Pyrene Studied by Emission and Transient Absorption Measurements

Table 1

Photophysical parameters for pyrene and perylene derivatives obtained in the present work.

Compound	ε/10^4  dm^3·mol^−1·cm^−1a	𝐸𝑆/kcal mol^−1b	Φ𝑓^c	𝜏𝑓/ns^d	𝑘𝑓/10^6 s^−1e	Φ^fnr	𝑘nr/10^6 s^−1g	𝐸𝑇/kcal mol^−1h	∑𝜉^2/10^4 cm^−2i	𝜆^T-Tmax/nm^j	𝜏T-T/μs^k
	(λ/nm)
pyrene	3.25 (335)	76.7	0.64	443	1.4	0.36	0.81	48.5	1.64	410	12.0
BuEPy	3.68 (362)	74.0	0.45	145	3.1	0.55	3.8	45.1	2.25	425	23.7
TMSEPy	4.35 (366)	74.0	0.70	89.2	7.9	0.30	3.4	—^l	3.84	430	12.5
TMSBPy	3.81 (381)	74.0	0.70	6.9	101	0.30	43	—^l	4.05	450	12.2

aThe molar absorptivities at the wavelength, λ nm.
bThe lowest excited singlet state energies estimated from the origins of absorption and fluorescence spectra.
cFluorescence quantum yields at 295 K.
dFluorescence lifetimes in cyclohexane at 295 K.
eFluorescence rates estimated by the equation 𝑘_𝑓=Φ_𝑓𝜏_𝑓⁻¹.
fEstimated by the equation Φ_nr=1−Φ_𝑓.
gRates of nonradiative processes were determined by the equation 𝑘_nr=Φ_nr𝜏_𝑓⁻¹.
hThe triplet energy was determined from the origin of the phosphorescence spectrum obtained in a mixture of methylcyclohexane and isopentane at 77 K.
iSum of the squared spin-orbit coupling constant (ζ) values.
jWavelengths of the maximum absorbance of the triplet-triplet absorption in cyclohexane at 295 K.
kTriplet lifetimes in CH at 295 K.
lNot determined.