By Victoria Waldersee and Christoph Steitz BERLIN/FRANKFURT (Reuters) – BASF will take a 7.3 billion euro ($7.9 billion) writedown as its Wintershall Dea energy business pulls out of Russia, the German chemicals giant said, triggering a net loss for 2022 and sending its shares lower. Wintershall Dea has deep ties to Russia, including stakes in the Nord Stream gas pipelines and joint ventures with Russia’s Gazprom. Russian billionaire Mikhail Fridman’s investment firm LetterOne owns a 27.3% stake in it. “Wintershall Dea will end its Russian activities. Continuing to operate in Russia is not ten…