Photophysics of pyrazine and its methylated derivatives at high pressure

Journal Article · Thu Mar 01 04:00:00 EST 1979 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.437755· OSTI ID:6281345

Mitchell, D J; Schuster, G B; Drickamer, H G

Fluorescence quantum yields and phosphorescence quantum yields and lifetimes were measured for pyrazine, 2, 6, dimethylpyrazine (DMP) and tetramethylpyrazine (TMP) in polymethyl methacrylate (PMMA) over the pressure range 20--120 kilobar. An additional low energy emission appeared at high pressure in these samples and in crystalline pyrazine. This is attributed to excimer fluorescence. The fluorescence yield increased with pressure at low pressures for all three materials, but exhibited a distinct maximum in pyrazine, a weak one in DMP and a monotonic increase in TMP. The behavior is attributed to increasing ..pi..--..pi..* character of the fluorescence balanced by increased excimer formation. The pressure effect on excimer emission is strongest in pyrazine and essentially nonexistent in TMP. For pyrazine the quantum yield for intersystem crossing (at 120 K) decreases with increasing pressure, while for TMP it remains near 1.0 at all pressures. This difference in behavior may be associated with different pressure effects on excimer formation noted above or to differences in the excimer peak location vis a vis the phosphorescence. In pyrazine it lies some 4--5000 cm/sup -1/ below the phosphorescence peak so that excimer to T/sub 1/ transfer is difficult, while in TMP the two peaks are nearly isoenergetic so that the transfer is possible.

• Research Organization: School of Chemical Sciences and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
• OSTI ID: 6281345
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 70:5; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
640300 -- Atomic
Molecular & Chemical Physics
74 ATOMIC AND MOLECULAR PHYSICS
AZINES
DATA
EMISSION SPECTROSCOPY
EXPERIMENTAL DATA
FLUORESCENCE SPECTROSCOPY
HETEROCYCLIC COMPOUNDS
INFORMATION
LIFETIME
LUMINESCENCE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORESCENCE
POLYMERS
PYRAZINES
SPECTROSCOPY
VERY HIGH PRESSURE