Question

Report the HOMO/LUMO energy gap for each molecule.

Calculate the corresponding wavelength for each energy difference.

Arrange the dye molecules in order of increasing wavelength.

Does this trend agree with the trend observed in Part 3 of this lab? What is the HOMO/LUMO gap dependent on ?

Data and Results

1,1'-diethyl-4,4'-cyanine iodide

1,1'-diethyl-4,4'-carbocyanine iodide

1,1'-diethyl-4,4'-dicarbocyanine iodide

HOMO (eV)

-9.813

-9.133

-8.766

LUMO (eV)

-2.339

-2.236

-2.189

respectively

Answer 1

Let us assume that

Compd​​1 = 1,1'-diethyl-4,4'-cyanine iodide

Compd​​2 = 1,1'-diethyl-4,4'-carbocyanine iodide

Compd​​3 = 1,1'-diethyl-4,4'-dicarbocyanine iodide

Increasing wavelength:-

Compd​​C1<Compd​​2<Compd​​3

∆E depend on the amount of energy that is required so that e- can exite from lower energy level(HOMO) to higher energy level(LUMO). And ∆E decreases as the conjugate within the compound increses. If conjugate is there, then the energy gap between LUMO and HOMO decreses. Energy is inversely proportional to wavelength.

2 3 Data & Result Compound :- Honde) 1,1-diethyl-4,4-cyanine hocice LUMO(a) AE= Elmo Enomo = he/st (m) - 9.813 -2.339 1, 1-diethyl-4,4'- carbocyanine ialide 7.42hed 16540 -9.132 -2.236 6.857 ev 173 34 .I'- chietinyl-4.4'- diterbogenine indide -8.766 -2.183 6.577 ev 189.32 ), : hele = 6.610-34) (3x108 mot). 1.38X10*2m 1.6541X10m 165.41X10m 16548 mm 7.474 x (1.602X10-1931) 197X10* : heyat 66X10*34J5) (3x 108ms) 198X1825 , 1.7934*102 173.34X10 9 => 79.34 6857 X 1.802 X109) 1. 047101 Agi helse: 66.61013) (3x108ms'). 4.381107m, 18792x107187.92x107187.32 mm 6597 (.602 X 10-191) 10536X10 Torder: , <^₂ <); \ - LUMO - HOME