Evolution of various physical properties of finite conjugated systems with increasing molecular size is studied using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method. We usually observe a transition from the finite to the infinite regime for surprisingly short molecular chains containing only 20-30 monomer units of cis-butadiene, cyclopentadiene, pyrrole, furan, and thiophene. Such a fast convergence of equilibrium geometries, induced atomic charges, electron densities of states (DOS) and energy gaps, dipole and quadrupole moments, and polarizabilities is particularly striking considering the presence of strong p-conjugation.Convergence in the size evolution of majority of molecular properties of conjugated systems occurs for surprisingly short molecular chains.

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