The field of metal-nucleic acid chemistry has now expanded beyond the fundamental science and biomedical applications of metal-nucleic acid interactions to tackle new problems in nanochemistry. This talk focuses on developing atomically precise and programmable DNA-metal nanomaterials to address challenges in biophotonics and bioelectronics. In particular, we investigate the nucleobase-specific interactions of Ag(I) with DNA. Recent studies showed that DNA duplexes can form entirely by Ag(I)-mediated base pairing, but their formation mechanisms are understudied. We combine temperature-controlled electronic circular dichroism (CD) spectroscopy with native mass spectrometry (MS) to monitor Ag(I)-DNA duplexation and enable the first nanomechanical studies of Ag(I)-DNA duplex stiffness. Under certain conditions, we find that Ag(I)-DNA duplexes assemble higher-order "wires" that could expand DNA nanostructures beyond canonical base pairing. We also use Ag(I)-DNA complexes as precursors for chemical synthesis of atomically precise silver nanoclusters (AgN-DNAs). These nanoclusters come in a diversity of bright, sequence-selected fluorescence colors and hold promise for bioimaging, but their structure-property relationships have remained elusive. By combining high-throughput experiments and machine learning models with analytical studies of single nanocluster species, we show how nucleobase sequence selects the structures and colors of AgN-DNAs. This approach enables the design of new DNA template sequences for AgN-DNAs emissive in the near-infrared tissue transparency window, a key area of need for bioimaging. Finally, I will discuss how we are using native MS and CD to advance understanding of AgN-DNA ligand chemistry. Our discovery of a new class of AgN-DNAs with additional halide ligands recently enabled the first electronic structure calculations for AgN-DNAs and presents new opportunites to expand these emitters for biophotonics applications.