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We present submillimeter spectra of the (proto-)super star cluster (SSC)candidates in the starbursting center of the nearby galaxy NGC 253 identifiedby Leroy et al. (2018). The 2.5pc resolution of our ALMA cycle 3 observationsapproach the size of the SSCs and allows the study of physical and chemicalproperties of the molecular gas in these sources. In the 14 SSC sources and inthe frequency ranges 342.0-345.8 GHz and 353.9-357.7 GHz we detect 55 linesbelonging to 19 different chemical species. The SSCs differ significantly inchemical complexity, with the richest clusters showing 19 species and the leastcomplex showing 4 species. We detect HCN isotopologues and isomers (H$^{13}$CN,HC$^{15}$N, H$^{15}$NC), abundant HC$_3$N, SO and S$^{18}$O, SO$_2$, andH$_2$CS. The gas ratios CO/HCN, CO/HCO$^+$ are low, ~1-10, implying high densegas fractions in the SSCs. Line ratio analyses suggests chemistry consistentwith photon-dominated regions and mechanical heating. None of the SSCs near thegalaxy center show line ratios that imply an X-ray dominated region, suggestingthat heating by any (still unknown) AGN does not play a major role. The gastemperatures are high in most sources, with an average rotational temperatureof ~130 K in SO$_2$. The widespread existence of vibrationally excited HCN andHC$_3$N transitions implies strong IR radiation fields, potentially trapped bya greenhouse effect due to high continuum opacities.

The Molecular ISM in the Super Star Clusters of the Starburst NGC 253