02444nas a2200265   4500008004100000022001400041245010200055210006900157260000800226300001100234490000700245520157000252653002401822653001501846653002401861653002001885653002401905100002001929700001601949700002601965700001901991700002002010700002602030856012202056       2026                        eng d  a1861-472800aFrom brittle to elastic: substituent effects on mechanical flexibility in aromatic amide crystals0 aFrom brittle to elastic substituent effects on mechanical flexib  cMAY  ae707950 v213 a<p>
	Mechanical flexibility in molecular crystalline materials represents a compelling paradigm shift from the long-held perception of crystals as inherently brittle solids. Herein, we demonstrate a brittle-to-elastic transition by subtle molecular modification in a pair of structurally analogous aromatic amides; N-[(4-methoxyphenyl)methyl]formamide (N4MFA, Crystal 1) and N-benzylformamide (NBFA, Crystal 2). Despite their close structural similarity, Crystal 1 exhibits brittle fracture under minimal stress, whereas Crystal 2 shows 1D elastic flexibility with reversible bending. Structural, computational, and mechanical analyses reveal that this contrast arises from substituent-controlled supramolecular packing. In Crystal 1, the methoxy (-OCH3) group promotes dense, anisotropic packing, leading to rigidity and fracture under stress. Removing the substituent in Crystal 2 enhances isotropy, pi-pi stacking, and interlocked packing, enabling reversible strain during elastic bending. Nanoindentation, energy framework, and elastic tensor analyses confirm this transition: Crystal 2 shows near-isotropic stiffness (E max/E min = 1.65) and interconnected energy networks, whereas Crystal 1 exhibits pronounced anisotropy (E max/E min = 3.95) and 1D cohesion. Hirshfeld surface analysis supports more balanced contacts in the elastic crystal. This work establishes a direct structure-mechanical correlation, showing that minor chemical modifications can tune flexibility and provide insights to guide the development of adaptive crystalline materials.</p>
10acrystal engineering10aElasticity10aMechanical property10ananoindentation10aresponsive crystals1 aBhowmik, Aritra1 aDas, Nirmal1 aSaxena, Ashish, Kumar1 aMishra, Kamini1 aBarsu, Nagaraju1 aMishra, Manish, Kumar  uhttps://library.ncl.res.in/content/brittle-elastic-substituent-effects-mechanical-flexibility-aromatic-amide-crystals01470nas a2200229   4500008004100000022001400041245009300055210006900148260000900217300000700226490000800233520072600241653001100967653001900978653002800997653002401025653001501049653001901064100001601083700002001099856012101119       2026                        eng d  a0974-362600aPhosphine radical cation catalysis for Markovnikov hydroamination of unactivated alkenes0 aPhosphine radical cation catalysis for Markovnikov hydroaminatio  cAPR   a510 v1383 a<p>
	Markovnikov-selective hydroamination of unactivated terminal alkenes has long remained a challenging transformation in C-N bond formation. Fan and co-workers1 addressed this using a metal-free phosphine photoredox system that operates via an unprecedented phosphine radical cation (P(IV)) mechanism, enabling alkene activation toward azole addition. This work highlights a powerful new strategy for C(sp3)-N bond construction beyond traditional transition-metal catalysis.Graphical abstractMetal-free phosphine photoredox catalysis enables Markovnikov-selective hydroamination of unactivated terminalalkenes via a novel phosphine radical cation mechanism, off ering a new strategy for C(sp3)-N bond formation.</p>
10aazoles10ahydroamination10aMarkovnikov selectivity10aPhosphine catalysis10aphotoredox10aradical cation1 aDas, Nirmal1 aBarsu, Nagaraju  uhttps://library.ncl.res.in/content/phosphine-radical-cation-catalysis-markovnikov-hydroamination-unactivated-alkenes