diff --git a/src/biotite/interface/rdkit/mol.py b/src/biotite/interface/rdkit/mol.py
index eb31a0854..21ccf9561 100644
--- a/src/biotite/interface/rdkit/mol.py
+++ b/src/biotite/interface/rdkit/mol.py
@@ -68,7 +68,7 @@ def to_mol(
     kekulize=False,
     use_dative_bonds=False,
     include_extra_annotations=(),
-    explicit_hydrogen=True,
+    explicit_hydrogen=False,
 ):
     """
     Convert an :class:`.AtomArray` or :class:`.AtomArrayStack` into a
@@ -103,6 +103,9 @@ def to_mol(
         explicit, i.e. each each hydrogen atom must be part of the :class:`AtomArray`.
         If set to false, the conversion process treats all hydrogen atoms as implicit
         and all hydrogen atoms in the :class:`AtomArray` are removed.
+        By default, explicit_hydrogen=False, i.e. hydrogen atoms are never assumed, to
+        avoid accidentally introducing radicals into the molecule upon calling
+        :func:`Chem.SanitizeMol()`.
 
     Returns
     -------
@@ -140,12 +143,24 @@ def to_mol(
     HXT
     """
     hydrogen_mask = atoms.element == "H"
+    _has_hydrogen = hydrogen_mask.any()
     if explicit_hydrogen:
-        if not hydrogen_mask.any():
+        if not _has_hydrogen:
             warnings.warn(
-                "No hydrogen found in the input, although 'explicit_hydrogen' is 'True'"
+                "No hydrogen found in the input, although 'explicit_hydrogen' is 'True'. "
+                "This may lead to unexpected results, as hydrogen atoms are not "
+                "implicitly added, which often results in radicals after sanitization "
+                "in RDKit. Make sure this is what you want.",
+                UserWarning,
             )
     else:
+        if _has_hydrogen:
+            warnings.warn(
+                "Hydrogen atoms are present in the input, although 'explicit_hydrogen' "
+                "is 'False'. All hydrogen atoms will be removed and then re-inferred "
+                "by RDKit. Make sure this is what you want.",
+                UserWarning,
+            )
         atoms = atoms[..., ~hydrogen_mask]
 
     mol = Chem.EditableMol(Chem.Mol())
@@ -290,14 +305,20 @@ def from_mol(mol, conformer_id=None, add_hydrogen=None):
         raise BadStructureError("Could not obtains atoms from Mol")
 
     if conformer_id is None:
-        conformers = [conf for conf in mol.GetConformers() if conf.Is3D()]
+        conformers = [conf for conf in mol.GetConformers()]
         atoms = AtomArrayStack(len(conformers), len(rdkit_atoms))
         for i, conformer in enumerate(conformers):
-            atoms.coord[i] = np.array(conformer.GetPositions())
+            if conformer.Is3D():
+                atoms.coord[i] = np.array(conformer.GetPositions())
+            else:
+                atoms.coord[i] = np.full((len(rdkit_atoms), 3), np.nan)
     else:
         conformer = mol.GetConformer(conformer_id)
         atoms = AtomArray(len(rdkit_atoms))
-        atoms.coord = np.array(conformer.GetPositions())
+        if conformer.Is3D():
+            atoms.coord = np.array(conformer.GetPositions())
+        else:
+            atoms.coord = np.full((len(rdkit_atoms), 3), np.nan)
 
     extra_annotations = defaultdict(
         # Use 'object' dtype first, as the maximum string length is unknown
@@ -363,7 +384,25 @@ def from_mol(mol, conformer_id=None, add_hydrogen=None):
             extra_annotations[annot_name][_atom_idx] = rdkit_atom.GetProp(annot_name)
 
     for annot_name, array in extra_annotations.items():
-        atoms.set_annotation(annot_name, array.astype(str))
+        # ... handle special case of implicit hydrogen atom flags
+        if annot_name == "isImplicit":
+            atoms.set_annotation(annot_name, array.astype(bool))
+            continue
+
+        # ... for all custom annotations, try numeric conversions in order of preference
+        for dtype in (bool, int, float):
+            try:
+                converted = array.astype(dtype)
+                # Verify the conversion was lossless by converting back
+                if np.array_equal(
+                    converted.astype(str), array.astype(str), equal_nan=True
+                ):
+                    atoms.set_annotation(annot_name, converted)
+                    break
+            except (ValueError, TypeError):
+                continue
+        else:  # ... if no numeric conversion succeeded
+            atoms.set_annotation(annot_name, array.astype(str))
 
     rdkit_bonds = list(mol.GetBonds())
     is_aromatic = np.array(