Expressions Calcullator

I've got this following class structure :

public abstract class AbstractExpression {...}

public class ConstExpression : AbstractExpression {...}
public class VarExpression : AbstractExpression {...}

public class AndExpression : AbstractExpression {...}
public class OrExpression : AbstractExpression {...}
public class XorExpression : AbstractExpression {...}

public class NotExpression : AbstractExpression {...}

And what I want to do now is split these expressions into two groups : Binary and Unary Expressions. I consider to make two abstract class inheriting the AbstractExpression class. I am looking for the best solution to convenient using this code in accordance with "interpreter" (behavioral design battern).