Question on Basic Strength

Which of the following compounds is the strongest nitrogen base and why?

Answer:

(3) is the least basic among the three as the nitrogen atom present in it is sp² hybridised while the nitrogen atoms in (1) and (2) are sp³ hybridised. sp² hybridised atom will have less tendency to donate electrons compared to an atom which is sp³ hybridised as the s-character in sp² hybrid orbitals are more. Comparing (1) and (2) the availability of electrons in nitrogen atom in compound (2) will be decreased by the presence of oxygen atom in the molecule. So, (1) is the strongest nitrogen base as the availability of electrons are more on the nitrogen atom in that molecule.