MMM = 3
PHI = numpy.zeros((MMM,MMM))

a=np.array([ 0.71,  1.63,  0.85])
b=np.array([ 0.24,  0.14, -0.03])
for k in range(0,MMM):
    F = 1j*a[k]/b[k]
    PHI[(k),(k)] = F

can't convert complex to float

[[ 2.95833333333j  0.  0.]
 [ 0.  11.6428571429j  0.]
 [ 0.  0.  28.3333333333j]]