Measurements of the optical properties of (NH 3 (CH 2 ) 7 NH 3 ) 2 Sn 3 I 10 confirm visible light absorption and photoluminescence but with a significant Stokes shift. UV-visible diffuse reflectance spectroscopy of a powder sample reveals a sharp onset of light absorption, with a tangent line of the pseudo-absorbance (k/s) extrapolated to an optical bandgap of 1.86(1) eV (664 nm), as presented in Figure (a). Tauc analysis assuming direct or indirect gaps for parabolic bands yields 1.91(1) eV or 1.81(1) eV, respectively (Figure ). The tailing of the absorption below the extrapolated band gap suggests the presence of a significant concentration of optically accessible defects, as is common to many Sn(II) derived semiconductors. Photoluminescence spectroscopy reveals a broad emission spectrum centered at 1.90(1) eV (650 nm) Figure (b), which coincides with the absorption onset.