scholarly journals Excited-State Distortions of Cyclometalated Ir(III) Complexes Determined from the Vibronic Structure in Luminescence Spectra

2007 ◽  
Vol 111 (17) ◽  
pp. 3256-3262 ◽  
Author(s):  
Xianghuai Wang ◽  
Jian Li ◽  
Mark E. Thompson ◽  
Jeffrey I. Zink
Keyword(s):  
Excited State ◽  
Luminescence Spectra ◽  
Vibronic Structure

Luminescence spectra and basicity constants in the electronically excited state of 1-, 2-, and 1,2-substituted benzazoles

1976 ◽  
Vol 25 (5) ◽  
pp. 1387-1390
Author(s):  
N. A. Kazakova ◽  
N. N. Chipanina ◽  
V. I. Cherednichenko ◽  
S. M. Ponomareva ◽  
E. S. Domnina ◽  
...  
Keyword(s):  
Excited State ◽  
Luminescence Spectra ◽  
Electronically Excited State ◽  
Electronically Excited

The electronic absorption spectra of NH 2 and ND 2

1959 ◽  
Vol 251 (1002) ◽  
pp. 553-602 ◽  
Keyword(s):  
Excited State ◽  
Bond Length ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Electronic Absorption Spectra ◽  
Interaction Constant ◽  
Bending Vibration ◽  
Vibronic Structure ◽  
Linear Configuration ◽  
Centrifugal Distortion Constants

The absorption spectra of <super>14</super>NH 2 , <super>15</super>NH 2 and <super>14</super>ND 2 have been photographed in the region 3900 to 8300 A with a 21 ft. concave grating spectrograph. The radicals are produced by the flash photolysis of <super>14</super>NH 3 , <super>15</super>NH 3 and <super>14</super>ND 3 respectively. A detailed study of the <super>14</super>NH 2 - <super>15</super>NH 2 isotope shifts suggests that the molecule has a linear configuration in the excited state and that the spectrum consists of a long progression of the bending vibration in this state. These conclusions have been confirmed by detailed rotational and vibrational analyses of the 14NH2 and 14ND2 spectra. The spectra consist of type C bands for which the transition moment is perpendicular to the plane of the molecule. For NH2, sixteen bands of the progression (0, v'%, 0) <- (0, 0, 0) have been identified with v'% — 3, 4, ..., 18. In addition four bands of a subsidiary progression (1, v'2, 0) <- (0, 0, 0) have been found; these bands derive most of their intensity from a Fermi-type resonance between (0, v'2) 0) and (1, v2 —4, 0) levels in the excited state. The interaction constant W nl is 72 + 3 cm <super>-1</super>. For ND 2 , fourteen bands of the principal progression (v2 — 5 to 18) and one band of the subsidiary progression have been identified. The upper state vibration frequencies w?' and (i)' are 3325 cm <super>-1</super> and 622 cm <super>-1</super> for NH 2 and 2520 cm <super>-1</super> and 422 cm <super>-1</super> for ND 2 respectively. The bending frequencies are unusually low ; moreover, the anharmonicities of the bending vibration are unusually large and negative (x22—11.4 cm <super>-1</super> for NH 2 and 8.1 cm <super>-1</super> for ND 2 ). The origin of the system lies in the region o f 10000 cm <super>-1</super>. Ground-state rotational term values have been derived from observed com bination differences; values for the rotational constants Aooo, B'ooo and Cooo and for the centrifugal distortion constants D"A, D"b and D"0 have been determined. The bond lengths and bond angles for NH 2 and ND 2 agree and are 1.024 + 0.005 A and 103° 20' + 30' respectively. Small spin splittings have been observed. In the excited state an unusual type of vibronic structure has been found. Successive levels of the bending vibration consist alternately of 27, d , T, ... and ... vibronic sub-levels with large vibronic splittings. The origins of the vibronic sub-bands may be represented by the formula yf = Vq—GK2, where G is ~ 27 cm -1 for NH 2 and ~ 19 cm <super>-1</super> for ND 2 . The rotational levels show both spin and A-type doubling. No simple formula has been found to fit the energies o f the II, A, 0 and -T rotational levels; the 27 levels fit the formula F(N) = 1) — D N2(N + 1)2, though with a negative value for D . By extrapolating the B values for the 27 levels to = 0 we obtain B'00o = 8.7 8 cm <super>-1</super> for NH 2 and 4.4 1 cm<super>-1</super> for ND 2 . These values are consistent with a linear configuration with a bond length of 0.97 5 A. The significance of this short bond length is discussed. An explanation of the complex vibronic structure is given. The two combining states are both derived from an electronic II state which is split by electronic-vibrational coupling for the reasons advanced by Renner. A detailed correlation diagram is given. A quantitative treatment of this effect by Pople & Longuet-Higgins gives good agreement with the experimental data.

Effects of Temperature and Magnetic Fields on the Luminescence of Single Crystal (NH4)2TeCl6

1988 ◽  
Vol 43 (6) ◽  
pp. 555-560 ◽  
Author(s):  
K. Meidenbauer ◽  
G. Gliemann
Keyword(s):  
Excited State ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Slow Component ◽  
Excited Electronic State ◽  
Luminescence Spectra ◽  
Teller Distortion ◽  
Field Dependent ◽  
Jahn Teller ◽  
Jahn Teller Distortion

The optical absorption of (NH4)2TeCl6 in acetonitrile at room temperature and the luminescence (spectra, decay curves) of single crystal (NH4)2TeCl6 at 1.9 K ≤ T ≤ 180K and at applied magnetic fields H (0 ≤ H ≤ 6 T) are reported. The temperature dependence of the luminescence indicates the existence of a metastable excited state energetically by ~ 80 cm−1 below a second excited state. With H || <111> the decay curves are monoexponential with magnetic field dependent slopes. H ||<001> yields biexponential decay curves, each composed of a slow component corresponding to the decay at H = 0, and of a field dependent fast component. The experimental results can be explained by effects of a tetragonal Jahn-Teller distortion due to a strong coupling of the excited electronic state 3Tlu of the Te(IV) ions and Eg vibration modes.

Temperature- and pressure-dependent luminescence spectroscopy on the trans-[ReO2(pyridine)4]+ complex — Analysis of vibronic structure, luminescence energies, and bonding characteristics

2004 ◽  
Vol 82 (6) ◽  
pp. 1083-1091 ◽  
Author(s):  
John K Grey ◽  
Ian S Butler ◽  
Christian Reber
Keyword(s):  
Molecular Structure ◽  
Low Temperature ◽  
Room Temperature ◽  
Complex Analysis ◽  
Variable Pressure ◽  
Luminescence Spectroscopy ◽  
Luminescence Spectra ◽  
Vibronic Structure ◽  
Temperature Spectra ◽  
Temperature And Pressure

Resolved vibronic structure in electronic spectra provides a detailed view into how molecular structure changes after absorption or emission of a photon. We report temperature- and pressure-dependent luminescence spectra of trans-[ReO2(pyridine)4]I. Low-temperature spectra reveal long vibronic progressions in the totally symmetric O=Re=O (907 cm–1) and Re-pyridine (211 cm–1) stretching modes, indicating large structural displacements along these normal coordinates. The luminescence band maximum is at ca. 15 500 cm–1. Room-temperature spectra are somewhat less-resolved; however, intervals closely matching the O=Re=O frequency (~870 cm–1) persist at higher temperatures. The variable pressure spectra exhibit distinct changes in the vibronic patterns, and luminescence energies decrease by 16 ± 2 cm–1/kbar (1 bar = 100 kPa). Low-temperature spectra are modeled using two-dimensional potential energy surfaces to represent the initial and final electronic states, from which the quantitative normal coordinate offsets can be determined. We then adapt this model to the room-temperature, pressure-dependent data where it is possible to determine how the offsets and other important spectroscopic parameters vary with the pressure-induced changes of the molecular structure. Key words: trans-[ReO2(pyridine)4]I, low-temperature luminescence spectroscopy, high-pressure luminescence spectroscopy, vibronic structure, emitting state distortions.

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