<?php if( $molecules_of_the_month = get_terms( array( 'taxonomy' => 'molecules_of_the_month' ) ) ) :
foreach( $molecules_of_the_month as $month ) :
$summaryimage = get_field('summary_preview_image', 'term_' .$month->term_id );?>
<?php print_r($summaryimage);?>
<?php endforeach;
endif;
?>
Try that on its own, if it works, integrate it into your code
