4-Nitrophenol derivatives are interesting chromophores for nonlinear optics (NLO), being typical donor-acceptor system connected by pi conjugation. Due to the presence of the acidic phenolic proton, they also readily form salts with suitably selected organic and metallic bases. The so-formed l -nitrophenolates have increased molecular hyperpolarizabilities (beta). The phenolate and nitro oxygens are strong hydrogen bond accepters and the nitro group has a tendency to coordinate with metal centers. This opens up two different engineering routes to build NLO materials from these chromophores: (a) organic-organic and (b) metal-organic salts. This paper reviews the crystal packing and nonlinear optical (NLO) efficiency in nitrophenolate crystals engineered through these routes and presents the crystal structure of a new NLO efficient organic-organic salt. 1-hydroxy-3-methylpyridinium 3-hydroxy-2,4,6-trinitrophenolate (P2(1)) In this crystal both the multidipolar anion and dipolar cation are NLO chromophores. The anions form herringbone mediated chain with intra and intermolecular O-H . . . .O hydrogen bonds and the cations are attached to them through strong O-H . . . .O- hydrogen bonds.