Chapter 17, Problem 17.64P

Use the observed ${}^1\text{H}\text{NMR}$ data to decide whether C and its dianion are aromatic, antiaromatic, or not

aromatic. C shows $\text{NMR}$ signals at $-4.25\left(6\text{H}\right)\text{and}8.14-8.67\left(10\text{H}\right)\text{ppm}$. The dianion of C shows $\text{NMR}$

signals at $-3\left(10\text{H}\right)\text{and}21\left(6\text{H}\right)\text{ppm}$. Why are the signals shifted upfield (or downfield) to such a large 

extent?