```python
import numpy as np
from pyscf import gto, dft, lib
import os

# Define the molecule
mol = gto.Mole()
mol.atom = '''
    H 0 0 0
    H 0 0 0.74
'''
mol.basis = 'cc-pVDZ'
mol.build()

# Perform DFT calculation for state 1
state1 = dft.RKS(mol)
state1.chkfile = 'state1.chk'
state1.xc = 'B3LYP'
state1.kernel()

# Perform DFT calculation for state 2
state2 = dft.RKS(mol)
state2.chkfile = 'state2.chk'
state2.xc = 'B3LYP'
state2.kernel()

# Read MO coefficients and occupation numbers from chkfiles
mo_coeff1 = lib.chkfile.load('state1.chk', 'scf/mo_coeff')
mo_occ1 = lib.chkfile.load('state1.chk', 'scf/mo_occ')
mo_coeff2 = lib.chkfile.load('state2.chk', 'scf/mo_coeff')
mo_occ2 = lib.chkfile.load('state2.chk', 'scf/mo_occ')

# Calculate overlap between two determinants
s = mol.intor('int1e_ovlp')
overlap = np.dot(mo_coeff1.T, np.dot(s, mo_coeff2))

# Construct density matrices
dm1 = np.dot(mo_coeff1 * mo_occ1, mo_coeff1.T)
dm2 = np.dot(mo_coeff2 * mo_occ2, mo_coeff2.T)

# Calculate one-electron and two-electron part contributions
h1 = mol.intor('int1e_kin') + mol.intor('int1e_nuc')
j1, k1 = state1.get_jk(mol, dm1)
j2, k2 = state2.get_jk(mol, dm2)

# One-electron contribution
one_electron = np.einsum('ij,ji', dm2, h1)

# Two-electron contribution
two_electron = np.einsum('ij,ji', dm2, (j1 - 0.5 * k1 + j2 - 0.5 * k2))

# Calculate new total energy
new_total_energy = one_electron + two_electron

# Calculate effective electronic coupling
Hab = new_total_energy - 0.5 * (state1.e_tot + state2.e_tot)

# Print the results
print(f"Effective Electronic Coupling: {Hab} Hartree")

# Remove chkfiles
os.remove('state1.chk')
os.remove('state2.chk')
```