x
10
−
19
J
∙
10
9
nm
λ
= 516.48 nm
Disc
2
(7) (C
25
):
-0.19067 – (-0.26634) = .07567 Hartree x (27.211 eV)
= 2.06 eV x (1.602 x 10
-19
J)
= 3.30 x 10
-19
J
λ
=
(
6.626
x
10
−
34
m
2
kg
/
s
)(
3
x
10
8
km
/
s
)
3.30
x
10
−
19
J
∙
10
9
nm
λ
= 602.62 nm
Hartree-Fock
λ
Calculation
Disc
2
(1) (C
19
):
-0.06487 – (-0.39016) = .32529 Hartree x (27.211 eV)
= 8.85 eV x (1.602 x 10
-19
J)
= 1.42 x 10
-18
J
λ
=
(
6.626
x
10
−
34
m
2
kg
/
s
)(
3
x
10
8
km
/
s
)
1.42
x
10
−
18
J
∙
10
9
nm
λ
= 140.18 nm
Disc
2
(3) (C
21
):
-0.07689 – (-0.36389) = .287 Hartree x (27.211 eV)
= 7.81 eV x (1.602 x 10
-19
J)
= 1.25 x 10
-18
J
λ
=
(
6.626
x
10
−
34
m
2
kg
/
s
)(
3
x
10
8
km
/
s
)
1.25
x
10
−
18
J
∙
10
9
nm
λ
= 158.89 nm
Disc
2
(5) (C
23
):
-0.08081 – (-0.34311) = .2623 Hartree x (27.211 eV)
= 7.14 eV x (1.602 x 10
-19
J)
= 1.14 x 10
-18
J
λ
=
(
6.626
x
10
−
34
m
2
kg
/
s
)(
3
x
10
8
km
/
s
)
1.14
x
10
−
18
J
∙
10
9
nm
λ
= 173.85 nm
Disc
2
(7) (C
25
):
-0.08696 – (-0.32439) = .23743 Hartree x (27.211 eV)
= 6.46 eV x (1.602 x 10
-19
J)
= 1.04 x 10
-18
J

λ
=
(
6.626
x
10
−
34
m
2
kg
/
s
)(
3
x
10
8
km
/
s
)
1.04
x
10
−
18
J
∙
10
9
nm
λ
= 192.06 nm
Conclusion
For each dye, the HOMO-LUMO gap was obtained using the B3LYP and Hartree-Fock calculation
using the WebMO interface with Gaussian 09 program. Results and calculations can be found in
the Results section of this report. The max wavelength of these dyes was then found using the
CIS and TD-DFT calculations. ZINDO was also used to find a quick CIS calculation of each dye. CIS
was then ran after to obtain more precise results. Graphs can be found for these calculations in
the Results section of this report.
Based on the graphs for CIS and TD-DFT, the R value and slope are the determining point of
which program carried out a more powerful estimated value of the max wavelength. CIS was
the more powerful method because the slope, 0.5173, was closer to a 1:1 ratio. The slope that
is closer to one is better correlated, therefore more accurately measures the maximum
wavelength on the computed and experimental values. The R value for CIS, 0.998, has little to
no variance, which would show a strong relationship between the experimental and computed
wavelengths. TD-DFT was not too far off from CIS, with a slope of 0.4855 and R value of 0.995.
A trend that agrees with the experimental data of this lab is that the dye with a longer carbon
chain has higher wavelengths. This trend is found all throughout this lab with all the calculated
programs that were ran for each dye. A source of error could have been from the splitting up
into groups for each dye. One group could have run a program wrong, thus giving miscalculated
HOMO-LUMO values or maximum wavelength values. This would then throw off results for the
calculated wavelengths in table one and graphs one and two. If these values were incorrect, the
graphs would then have skewed slope and R values.
Based off all data collected, CIS was the more powerful method of estimating the value of the
maximum wavelength compared to the HOMO-LUMO gap. The computed data was found by
the WebMO interface using the Gaussian 09 program
References
Macrae, Roderick M. “Spectra of Conjugated Dyes 2: Calculation of Spectra.”
2019. (aka Lab Handout)

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- Fall '19
- Quantum Chemistry, Computational chemistry