With "syms" the created matrix is symbolic, then it contains symbolic variables. The names of these variables must follow the standard rules of Matlab: less than 64 characters, only letters, numbers and the underscore, but the first character must be a letter. Therefore 'c080' is valid, while '80c0' is not.
What do you want to achieve? Hexadecimal values are stored as strings, so you either need a cell string or perhaps storing the values in the usual decimal format is the most direct solution. But syms seems to be not sufficient for the job.
