Nan values in columns when creating a dataframe

I try to create a dataframe with columns. I import values of these columns from other dataframe that are not empty. But when i create it,, i get an empty dataframe with Nan VAlues .

Here the code :

# initialize data of lists.
comparaison = {'actual': imp_all['prix_moyen'].tail(100),
        'predicted': best_model.fittedvalues.tail(100)}

print(comparaison)
  
# Creates pandas DataFrame.
df = pd.DataFrame(comparaison, index = pd.date_range(start='2022-08-25', periods=100))

print(df)

Result :

{'actual': 1149    0.001313
1150    0.001381
1151    0.001297
1152    0.001412
1153    0.001480
          ...   
1244    0.001474
1245    0.001467
1246    0.001492
1247    0.001530
1248    0.001424
Name: prix_moyen, Length: 100, dtype: float64, 'predicted': 1149    0.001371
1150    0.001340
1151    0.001342
1152    0.001306
1153    0.001377
          ...   
1244    0.001477
1245    0.001393
1246    0.001354
1247    0.001326
1248    0.001356
Length: 100, dtype: float64}
            actual  predicted
2022-08-25     NaN        NaN
2022-08-26     NaN        NaN
2022-08-27     NaN        NaN
2022-08-28     NaN        NaN
2022-08-29     NaN        NaN
...            ...        ...
2022-11-28     NaN        NaN
2022-11-29     NaN        NaN
2022-11-30     NaN        NaN
2022-12-01     NaN        NaN
2022-12-02     NaN        NaN

[100 rows x 2 columns]

Can you help me to fix this error?

thanks