In this work, we describe the second-order nonlinear optical (NLO) properties of a number of chromophores that feature transition metal ions in classic coordination environments. We focused our attention on the advantages of these species over standard hyperpolarizable chromophores based on conventional all-organic frameworks. For example, studies of Ruthenium(II)-based electron donor-acceptor (D-A) polyenes illustrate that transition metal-based compounds can show atypical conjugation-length dependences of the observed hyperpolarizability relative to closely related organic NLO chromophores. Likewise, the second-order NLO responses observed for highly conjugated (polypyridyl)metal(phorphinato)zinc(II) chromophores can be extraordinarily large, illustrating how coupled oscillator photophysics can be exploited to design materials with record hyperpolarizabilities at telecommunication-relevant wavelengths. Finally, our work demonstrates that the presence of a transition metal ion in NLO chromophores makes possible new strategies to switch and gate NLO responses voltammetrically.