deserialization – Json deserializea rtf file

I have been searching the web trying to understand what is happening. I have a rtf file with data and format tags used to generate a .doc report. Due the size I am trying to serialize it and pass to a API.
The serialization seems to be working ok but when I try do deserialize it it gives me the error: Invalid property identifier character: . Path ”, line 1, position 1.
here is part of the serialized file(just the beginning due the size of it):

“{rtf1deff0 stshfdbch1stshfloch1stshfhich1stshfbi1{fonttbl{f0 Calibri;}{f1 Times New Roman;}{f2 Calibri Light;}{f3 Arial;}{f4 Arial Narrow;}{f5 Segoe UI;}}{colortbl ;red0green0blue255 ;red0green0blue0 ;red176green0blue45 ;red104green102blue92 ;red255green255blue255 ;red242green242blue242 ;}{defchp fcs1f1fcs1f1dbchaf1hichaf1lochaf1cgrid1fs22}{stylesheet {snext0qlsa120fcs1f1fcs1f1dbchaf1hichaf0lochaf0fs22lang3081langnp3081 Normal;}{s1sbasedon0qlfcs1f1fcs1f1dbchaf1hichaf1lochaf1fs20 footnote text;}{s2sbasedon0qlfcs1f1fcs1f1dbchaf1hichaf1lochaf1fs20 endnote text;}{s3sbasedon0snext0sqformatqloutlinelevel0sb240sa60fcs1f1fcs1f1dbchaf1hichaf2lochaf2fs32lang3081langnp3081b heading 1;}{s4sbasedon0snext0sqformatqloutlinelevel1sb240sa60fcs1f1fcs1f1dbchaf1hichaf2lochaf2fs28lang3081langnp3081bi heading 2;}{s5sbasedon0snext5sqformatqlfcs1f1fcs1f1dbchaf1hichaf0lochaf0fs22lang3081langnp3081 No Spacing;}{s6sbasedon0snext6qjtqctx4153tqrtx8306fcs1f1fcs1f1dbchaf1hichaf3lochaf3fs22lang3081langnp3081 header;}{s7sbasedon0snext7qjfcs1f1fcs1f1dbchaf1hichaf4lochaf4fs16lang3081langnp3081 Body Text;}{s8sbasedon0snext8qltqctx4513tqrtx9026fcs1f1fcs1f1dbchaf1hichaf0lochaf0fs22lang3081langnp3081 footer;}{s9sbasedon0snext0sqformatqloutlinelevel0sb120fcs1f1fcs1f1dbchaf1hichaf0lochaf0fs28lang3081langnp3081capsb Title;}{s10sbasedon0snext10qlfcs1f1fcs1f1dbchaf1hichaf5lochaf5fs18lang3081langnp3081 Balloon Text;}{cs11fcs1f1fcs1f1dbchaf1hichaf1lochaf1fs22 Default Paragraph Font;}

Any ideas please? Thanks