Include Curly brackets into String CURL

My problem falls on the use of curly brackets on the URL. This URL is intended to post information to a given data base and in case of success it returns TRUE.
The point is that every time I use these brackets to form a jason array the curl command is not generated correctly due to no response of the server is done.

I have also tried to send the hexa value of the brackets (%5B%7B%7D%5D ) but either not work.

If someone could provide and example curl command with curly brackets inside the URL and the proper atributtes used ( -g for example) it would be usefull for me.

Thanks