  We study the influence of different metallicities on the physical, thermal,
and chemical properties of protoplanetary disks, and in particular on the
formation and destruction of carbon-based molecules. With the thermo-chemical
code ProoDIMO we investigate the impact of lower metallicities on the radiation
field, disk temperature, and the abundance of different molecules (H$_2$O,
CH$_4$, CO, CO$_2$, HCN, CN, HCO$^+$ and N$_2$H$^+$). We use a fiducial disk
model as a reference model and produce two models with lower metallicity. The
resulting influence on different chemical species is studied by analyzing their
abundance distribution throughout the disk and their vertical column density.
Furthermore, the formation and destruction reactions of the chemical species
are studied. The results show a relation between the metallicity of the disk
and the strength of the stellar radiation field inside the disk. As the
metallicity decreases the radiation field is able to penetrate deeper regions
of the disk. As a result, there is a stronger radiation field overall in the
disk with lower metallicity which also heats up the disk. This triggers a
series of changes in the chemical formation and destruction efficiencies for
different chemical species. In most cases, the available species abundances
change and have greater values compared to scaled-down abundances by constant
factors. Metallicity has a clear impact on the snowline of the molecules
studied here as well. As metallicity decreases the snowlines are pushed further
out and existing snow rings shrink in size.
